21457625661 has 24 divisors (see below), whose sum is σ = 32665295520. Its totient is φ = 13535708256.

The previous prime is 21457625647. The next prime is 21457625677. The reversal of 21457625661 is 16652675412.

21457625661 is a `hidden beast` number, since 2 + 14 + 5 + 7 + 625 + 6 + 6 + 1 = 666.

It is not a de Polignac number, because 21457625661 - 2¹⁷ = 21457494589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21457623661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 65551 + ... + 217283.

It is an arithmetic number, because the mean of its divisors is an integer number (1361053980).

Almost surely, 2^21457625661 is an apocalyptic number.

It is an amenable number.

21457625661 is a deficient number, since it is larger than the sum of its proper divisors (11207669859).

21457625661 is a wasteful number, since it uses less digits than its factorization.

21457625661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152585 (or 152582 counting only the distinct ones).

The product of its digits is 604800, while the sum is 45.

The spelling of 21457625661 in words is "twenty-one billion, four hundred fifty-seven million, six hundred twenty-five thousand, six hundred sixty-one".