15640516756981 has 2 divisors, whose sum is σ = 15640516756982. Its totient is φ = 15640516756980.

The previous prime is 15640516756979. The next prime is 15640516757009. The reversal of 15640516756981 is 18965761504651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14552164972900 + 1088351784081 = 3814730^2 + 1043241^2 .

It is a cyclic number.

It is not a de Polignac number, because 15640516756981 - 2¹ = 15640516756979 is a prime.

It is a super-2 number, since 2×15640516756981² (a number of 27 digits) contains 22 as substring.

Together with 15640516756979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15640516756681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7820258378490 + 7820258378491.

It is an arithmetic number, because the mean of its divisors is an integer number (7820258378491).

Almost surely, 2^{15640516756981} is an apocalyptic number.

It is an amenable number.

15640516756981 is a deficient number, since it is larger than the sum of its proper divisors (1).

15640516756981 is an equidigital number, since it uses as much as digits as its factorization.

15640516756981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 54432000, while the sum is 64.

The spelling of 15640516756981 in words is "fifteen trillion, six hundred forty billion, five hundred sixteen million, seven hundred fifty-six thousand, nine hundred eighty-one".