21624987 has 16 divisors (see below), whose sum is σ = 29445632. Its totient is φ = 14113440.

The previous prime is 21624973. The next prime is 21625027. The reversal of 21624987 is 78942612.

It is not a de Polignac number, because 21624987 - 2⁴ = 21624971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21624937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54273 + ... + 54669.

It is an arithmetic number, because the mean of its divisors is an integer number (1840352).

Almost surely, 2^21624987 is an apocalyptic number.

21624987 is a deficient number, since it is larger than the sum of its proper divisors (7820645).

21624987 is a wasteful number, since it uses less digits than its factorization.

21624987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738.

The product of its digits is 48384, while the sum is 39.

The square root of 21624987 is about 4650.2674116657. The cubic root of 21624987 is about 278.6026769492.

The spelling of 21624987 in words is "twenty-one million, six hundred twenty-four thousand, nine hundred eighty-seven".