21538913265 has 48 divisors (see below), whose sum is σ = 37777678848. Its totient is φ = 11351708928.

The previous prime is 21538913261. The next prime is 21538913269. The reversal of 21538913265 is 56231983512.

21538913265 is a `hidden beast` number, since 2 + 1 + 5 + 389 + 1 + 3 + 265 = 666.

It is an interprime number because it is at equal distance from previous prime (21538913261) and next prime (21538913269).

It is not a de Polignac number, because 21538913265 - 2² = 21538913261 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21538913265.

It is not an unprimeable number, because it can be changed into a prime (21538913261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1366962 + ... + 1382628.

It is an arithmetic number, because the mean of its divisors is an integer number (787034976).

Almost surely, 2^21538913265 is an apocalyptic number.

It is an amenable number.

21538913265 is a deficient number, since it is larger than the sum of its proper divisors (16238765583).

21538913265 is a wasteful number, since it uses less digits than its factorization.

21538913265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16038 (or 16035 counting only the distinct ones).

The product of its digits is 388800, while the sum is 45.

The spelling of 21538913265 in words is "twenty-one billion, five hundred thirty-eight million, nine hundred thirteen thousand, two hundred sixty-five".