21010556657 has 2 divisors, whose sum is σ = 21010556658. Its totient is φ = 21010556656.

The previous prime is 21010556639. The next prime is 21010556659. The reversal of 21010556657 is 75665501012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19991414881 + 1019141776 = 141391^2 + 31924^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010556657 - 2²² = 21006362353 is a prime.

Together with 21010556659, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21010556657.

It is not a weakly prime, because it can be changed into another prime (21010556659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505278328 + 10505278329.

It is an arithmetic number, because the mean of its divisors is an integer number (10505278329).

Almost surely, 2^21010556657 is an apocalyptic number.

It is an amenable number.

21010556657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010556657 is an equidigital number, since it uses as much as digits as its factorization.

21010556657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63000, while the sum is 38.

The spelling of 21010556657 in words is "twenty-one billion, ten million, five hundred fifty-six thousand, six hundred fifty-seven".