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70 (number)
70 (seventy) is the natural number following 69 and preceding 71.
70 is the fourth discrete sphenic number, as the first of the form . It is the smallest weird number, a natural number that is abundant but not semiperfect, where it is also the second-smallest primitive abundant number, after 20. 70 is in equivalence with the sum between the smallest number that is the sum of two abundant numbers, and the largest that is not (24, 46).
70 is the tenth Erdős–Woods number, since it is possible to find sequences of seventy consecutive integers such that each inner member shares a factor with either the first or the last member. It is also the sixth Pell number, preceding the tenth prime number 29, in the sequence .
70 is a palindromic number in bases 9 (779), 13 (5513) and 34 (2234).
70 is the thirteenth happy number in decimal, where 7 is the first such number greater than 1 in base ten: the sum of squares of its digits eventually reduces to 1.
70 = 2 × 5 × 7 simplifies to 7 × 10, or the product of the first happy prime in decimal, and the base (10).
70 contains an aliquot sum of 74, in an aliquot sequence of four composite numbers (70, 74, 40, 50, 43) in the prime 43-aliquot tree.
The sum 43 + 50 + 40 = 133 represents the one-hundredth composite number, where the sum of all members in this aliquot sequence up to 70 is the fifty-ninth prime, 277 (this prime index value represents the seventeenth prime number and seventh super-prime, 59).
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70 (number)
70 (seventy) is the natural number following 69 and preceding 71.
70 is the fourth discrete sphenic number, as the first of the form . It is the smallest weird number, a natural number that is abundant but not semiperfect, where it is also the second-smallest primitive abundant number, after 20. 70 is in equivalence with the sum between the smallest number that is the sum of two abundant numbers, and the largest that is not (24, 46).
70 is the tenth Erdős–Woods number, since it is possible to find sequences of seventy consecutive integers such that each inner member shares a factor with either the first or the last member. It is also the sixth Pell number, preceding the tenth prime number 29, in the sequence .
70 is a palindromic number in bases 9 (779), 13 (5513) and 34 (2234).
70 is the thirteenth happy number in decimal, where 7 is the first such number greater than 1 in base ten: the sum of squares of its digits eventually reduces to 1.
70 = 2 × 5 × 7 simplifies to 7 × 10, or the product of the first happy prime in decimal, and the base (10).
70 contains an aliquot sum of 74, in an aliquot sequence of four composite numbers (70, 74, 40, 50, 43) in the prime 43-aliquot tree.
The sum 43 + 50 + 40 = 133 represents the one-hundredth composite number, where the sum of all members in this aliquot sequence up to 70 is the fifty-ninth prime, 277 (this prime index value represents the seventeenth prime number and seventh super-prime, 59).