21037961657 has 2 divisors, whose sum is σ = 21037961658. Its totient is φ = 21037961656.

The previous prime is 21037961629. The next prime is 21037961663. The reversal of 21037961657 is 75616973012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19427063161 + 1610898496 = 139381^2 + 40136^2 .

It is a cyclic number.

It is not a de Polignac number, because 21037961657 - 2²⁸ = 20769526201 is a prime.

It is not a weakly prime, because it can be changed into another prime (21037961557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10518980828 + 10518980829.

It is an arithmetic number, because the mean of its divisors is an integer number (10518980829).

Almost surely, 2^21037961657 is an apocalyptic number.

It is an amenable number.

21037961657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21037961657 is an equidigital number, since it uses as much as digits as its factorization.

21037961657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 476280, while the sum is 47.

The spelling of 21037961657 in words is "twenty-one billion, thirty-seven million, nine hundred sixty-one thousand, six hundred fifty-seven".