21587979 has 12 divisors (see below), whose sum is σ = 33483624. Its totient is φ = 12335904.

The previous prime is 21587963. The next prime is 21587987. The reversal of 21587979 is 97978512.

It is not a de Polignac number, because 21587979 - 2⁴ = 21587963 is a prime.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21587959) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 73282 + ... + 73575.

It is an arithmetic number, because the mean of its divisors is an integer number (2790302).

Almost surely, 2^21587979 is an apocalyptic number.

21587979 is a deficient number, since it is larger than the sum of its proper divisors (11895645).

21587979 is a wasteful number, since it uses less digits than its factorization.

21587979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146874 (or 146867 counting only the distinct ones).

The product of its digits is 317520, while the sum is 48.

The square root of 21587979 is about 4646.2865817769. The cubic root of 21587979 is about 278.4436569674.

The spelling of 21587979 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred seventy-nine".