21231972 has 36 divisors (see below), whose sum is σ = 54068560. Its totient is φ = 7024752.

The previous prime is 21231971. The next prime is 21231979. The reversal of 21231972 is 27913212.

It is a tau number, because it is divible by the number of its divisors (36).

It is not an unprimeable number, because it can be changed into a prime (21231971) 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 11 ways as a sum of consecutive naturals, for example, 2883 + ... + 7125.

Almost surely, 2^21231972 is an apocalyptic number.

It is an amenable number.

21231972 is an abundant number, since it is smaller than the sum of its proper divisors (32836588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21231972 is a wasteful number, since it uses less digits than its factorization.

21231972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4392 (or 4387 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21231972 is about 4607.8164025924. The cubic root of 21231972 is about 276.9045620812.

It can be divided in two parts, 2123 and 1972, that added together give a triangular number (4095 = T₉₀).

The spelling of 21231972 in words is "twenty-one million, two hundred thirty-one thousand, nine hundred seventy-two".