21256044564977 has 2 divisors, whose sum is σ = 21256044564978. Its totient is φ = 21256044564976.

The previous prime is 21256044564901. The next prime is 21256044565051. The reversal of 21256044564977 is 77946544065212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20764644966976 + 491399598001 = 4556824^2 + 700999^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256044564977 - 2⁸ = 21256044564721 is a prime.

It is a super-2 number, since 2×21256044564977² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21256044561977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628022282488 + 10628022282489.

It is an arithmetic number, because the mean of its divisors is an integer number (10628022282489).

Almost surely, 2^{21256044564977} is an apocalyptic number.

It is an amenable number.

21256044564977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256044564977 is an equidigital number, since it uses as much as digits as its factorization.

21256044564977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 101606400, while the sum is 62.

The spelling of 21256044564977 in words is "twenty-one trillion, two hundred fifty-six billion, forty-four million, five hundred sixty-four thousand, nine hundred seventy-seven".