21664545 has 64 divisors (see below), whose sum is σ = 42923520. Its totient is φ = 9105408.

The previous prime is 21664529. The next prime is 21664607. The reversal of 21664545 is 54546612.

It is not a de Polignac number, because 21664545 - 2⁴ = 21664529 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 94491 + ... + 94719.

It is an arithmetic number, because the mean of its divisors is an integer number (670680).

Almost surely, 2^21664545 is an apocalyptic number.

It is an amenable number.

21664545 is a deficient number, since it is larger than the sum of its proper divisors (21258975).

21664545 is a wasteful number, since it uses less digits than its factorization.

21664545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 314.

The product of its digits is 28800, while the sum is 33.

The square root of 21664545 is about 4654.5187721181. The cubic root of 21664545 is about 278.7724535661.

The spelling of 21664545 in words is "twenty-one million, six hundred sixty-four thousand, five hundred forty-five".