21637968665057 has 2 divisors, whose sum is σ = 21637968665058. Its totient is φ = 21637968665056.

The previous prime is 21637968665039. The next prime is 21637968665099. The reversal of 21637968665057 is 75056686973612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19853048616976 + 1784920048081 = 4455676^2 + 1336009^2 .

It is a cyclic number.

It is not a de Polignac number, because 21637968665057 - 2²⁰ = 21637967616481 is a prime.

It is a super-2 number, since 2×21637968665057² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21637968665557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10818984332528 + 10818984332529.

It is an arithmetic number, because the mean of its divisors is an integer number (10818984332529).

Almost surely, 2^{21637968665057} is an apocalyptic number.

It is an amenable number.

21637968665057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21637968665057 is an equidigital number, since it uses as much as digits as its factorization.

21637968665057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 685843200, while the sum is 71.

The spelling of 21637968665057 in words is "twenty-one trillion, six hundred thirty-seven billion, nine hundred sixty-eight million, six hundred sixty-five thousand, fifty-seven".