21640662425 has 12 divisors (see below), whose sum is σ = 26843774076. Its totient is φ = 17306496000.

The previous prime is 21640662419. The next prime is 21640662443. The reversal of 21640662425 is 52426604612.

It can be written as a sum of positive squares in 6 ways, for example, as 7994684569 + 13645977856 = 89413^2 + 116816^2 .

It is not a de Polignac number, because 21640662425 - 2⁴ = 21640662409 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 76976 + ... + 221825.

It is an arithmetic number, because the mean of its divisors is an integer number (2236981173).

Almost surely, 2^21640662425 is an apocalyptic number.

21640662425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21640662425 is a deficient number, since it is larger than the sum of its proper divisors (5203111651).

21640662425 is a wasteful number, since it uses less digits than its factorization.

21640662425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 301708 (or 301703 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 38.

The spelling of 21640662425 in words is "twenty-one billion, six hundred forty million, six hundred sixty-two thousand, four hundred twenty-five".