21428979 has 48 divisors (see below), whose sum is σ = 35750400. Its totient is φ = 11309760.

The previous prime is 21428971. The next prime is 21428989. The reversal of 21428979 is 97982412.

It is not a de Polignac number, because 21428979 - 2³ = 21428971 is a prime.

It is a super-2 number, since 2×21428979² = 918402281964882, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21428979.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428971) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 89542 + ... + 89780.

It is an arithmetic number, because the mean of its divisors is an integer number (744800).

Almost surely, 2^21428979 is an apocalyptic number.

21428979 is a deficient number, since it is larger than the sum of its proper divisors (14321421).

21428979 is a wasteful number, since it uses less digits than its factorization.

21428979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296 (or 285 counting only the distinct ones).

The product of its digits is 72576, while the sum is 42.

The square root of 21428979 is about 4629.1445213992. The cubic root of 21428979 is about 277.7583731097.

The spelling of 21428979 in words is "twenty-one million, four hundred twenty-eight thousand, nine hundred seventy-nine".