21506871465 has 32 divisors (see below), whose sum is σ = 38280211200. Its totient is φ = 11456599680.

The previous prime is 21506871409. The next prime is 21506871473. The reversal of 21506871465 is 56417860512.

21506871465 is a `hidden beast` number, since 2 + 1 + 506 + 87 + 1 + 4 + 65 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-21506871465 is a prime.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21506871465.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 18325 + ... + 208205.

It is an arithmetic number, because the mean of its divisors is an integer number (1196256600).

Almost surely, 2^21506871465 is an apocalyptic number.

It is an amenable number.

21506871465 is a deficient number, since it is larger than the sum of its proper divisors (16773339735).

21506871465 is a wasteful number, since it uses less digits than its factorization.

21506871465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190734 (or 190728 counting only the distinct ones).

The product of its (nonzero) digits is 403200, while the sum is 45.

The spelling of 21506871465 in words is "twenty-one billion, five hundred six million, eight hundred seventy-one thousand, four hundred sixty-five".