21640454075657 has 8 divisors (see below), whose sum is σ = 22394404254600. Its totient is φ = 20887019071744.

The previous prime is 21640454075519. The next prime is 21640454075671. The reversal of 21640454075657 is 75657045404612.

It can be written as a sum of positive squares in 4 ways, for example, as 2720137712656 + 18920316363001 = 1649284^2 + 4349749^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21640454075657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21640454075057) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 128708282 + ... + 128876307.

It is an arithmetic number, because the mean of its divisors is an integer number (2799300531825).

Almost surely, 2^{21640454075657} is an apocalyptic number.

It is an amenable number.

21640454075657 is a deficient number, since it is larger than the sum of its proper divisors (753950178943).

21640454075657 is a wasteful number, since it uses less digits than its factorization.

21640454075657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 257587515.

The product of its (nonzero) digits is 28224000, while the sum is 56.

The spelling of 21640454075657 in words is "twenty-one trillion, six hundred forty billion, four hundred fifty-four million, seventy-five thousand, six hundred fifty-seven".