21879944 has 16 divisors (see below), whose sum is σ = 43184400. Its totient is φ = 10364112.

The previous prime is 21879943. The next prime is 21879947. The reversal of 21879944 is 44997812.

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21879895 and 21879904.

It is not an unprimeable number, because it can be changed into a prime (21879943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71822 + ... + 72125.

It is an arithmetic number, because the mean of its divisors is an integer number (2699025).

Almost surely, 2^21879944 is an apocalyptic number.

It is an amenable number.

21879944 is a deficient number, since it is larger than the sum of its proper divisors (21304456).

21879944 is a wasteful number, since it uses less digits than its factorization.

21879944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143972 (or 143968 counting only the distinct ones).

The product of its digits is 145152, while the sum is 44.

The square root of 21879944 is about 4677.6002394390. The cubic root of 21879944 is about 279.6933036404.

The spelling of 21879944 in words is "twenty-one million, eight hundred seventy-nine thousand, nine hundred forty-four".