21579939 has 20 divisors (see below), whose sum is σ = 32391216. Its totient is φ = 14317776.

The previous prime is 21579931. The next prime is 21579947. The reversal of 21579939 is 93997512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21579931) and next prime (21579947).

It is not a de Polignac number, because 21579939 - 2³ = 21579931 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21579894 and 21579903.

It is not an unprimeable number, because it can be changed into a prime (21579931) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 20797 + ... + 21809.

Almost surely, 2^21579939 is an apocalyptic number.

21579939 is a deficient number, since it is larger than the sum of its proper divisors (10811277).

21579939 is a wasteful number, since it uses less digits than its factorization.

21579939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1288 (or 1279 counting only the distinct ones).

The product of its digits is 153090, while the sum is 45.

The square root of 21579939 is about 4645.4212941347. The cubic root of 21579939 is about 278.4090857989.

The spelling of 21579939 in words is "twenty-one million, five hundred seventy-nine thousand, nine hundred thirty-nine".