21931928 has 16 divisors (see below), whose sum is σ = 43287000. Its totient is φ = 10388736.

The previous prime is 21931927. The next prime is 21931933. The reversal of 21931928 is 82913912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21931927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71993 + ... + 72296.

Almost surely, 2^21931928 is an apocalyptic number.

It is an amenable number.

21931928 is a deficient number, since it is larger than the sum of its proper divisors (21355072).

21931928 is a wasteful number, since it uses less digits than its factorization.

21931928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144314 (or 144310 counting only the distinct ones).

The product of its digits is 7776, while the sum is 35.

The square root of 21931928 is about 4683.1536383083. The cubic root of 21931928 is about 279.9146338402.

The spelling of 21931928 in words is "twenty-one million, nine hundred thirty-one thousand, nine hundred twenty-eight".