21979615 has 16 divisors (see below), whose sum is σ = 30228480. Its totient is φ = 15029280.

The previous prime is 21979603. The next prime is 21979621. The reversal of 21979615 is 51697912.

It is not a de Polignac number, because 21979615 - 2¹¹ = 21977567 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16546 + ... + 17824.

It is an arithmetic number, because the mean of its divisors is an integer number (1889280).

Almost surely, 2^21979615 is an apocalyptic number.

21979615 is a deficient number, since it is larger than the sum of its proper divisors (8248865).

21979615 is a wasteful number, since it uses less digits than its factorization.

21979615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1782.

The product of its digits is 34020, while the sum is 40.

The square root of 21979615 is about 4688.2422079069. The cubic root of 21979615 is about 280.1173615155.

The spelling of 21979615 in words is "twenty-one million, nine hundred seventy-nine thousand, six hundred fifteen".