21916521 has 32 divisors (see below), whose sum is σ = 35798400. Its totient is φ = 13141440.

The previous prime is 21916513. The next prime is 21916529. The reversal of 21916521 is 12561912.

21916521 is a `hidden beast` number, since 2 + 1 + 9 + 1 + 652 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (21916513) and next prime (21916529).

It is not a de Polignac number, because 21916521 - 2³ = 21916513 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21916529) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 32035 + ... + 32711.

It is an arithmetic number, because the mean of its divisors is an integer number (1118700).

Almost surely, 2^21916521 is an apocalyptic number.

It is an amenable number.

21916521 is a deficient number, since it is larger than the sum of its proper divisors (13881879).

21916521 is a wasteful number, since it uses less digits than its factorization.

21916521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 806 (or 800 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 21916521 is about 4681.5084107582. The cubic root of 21916521 is about 279.8490725723.

The spelling of 21916521 in words is "twenty-one million, nine hundred sixteen thousand, five hundred twenty-one".