21239972 has 12 divisors (see below), whose sum is σ = 40029276. Its totient is φ = 9803040.

The previous prime is 21239969. The next prime is 21240001. The reversal of 21239972 is 27993212.

It can be written as a sum of positive squares in 2 ways, for example, as 7873636 + 13366336 = 2806^2 + 3656^2 .

It is a super-2 number, since 2×21239972² = 902272821121568, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 204179 + ... + 204282.

It is an arithmetic number, because the mean of its divisors is an integer number (3335773).

Almost surely, 2^21239972 is an apocalyptic number.

It is an amenable number.

21239972 is a deficient number, since it is larger than the sum of its proper divisors (18789304).

21239972 is a wasteful number, since it uses less digits than its factorization.

21239972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 408478 (or 408476 counting only the distinct ones).

The product of its digits is 13608, while the sum is 35.

The square root of 21239972 is about 4608.6844109789. The cubic root of 21239972 is about 276.9393360270.

The spelling of 21239972 in words is "twenty-one million, two hundred thirty-nine thousand, nine hundred seventy-two".