21438772 has 18 divisors (see below), whose sum is σ = 38862278. Its totient is φ = 10348128.

The previous prime is 21438757. The next prime is 21438779. The reversal of 21438772 is 27783412.

It can be written as a sum of positive squares in 3 ways, for example, as 6739216 + 14699556 = 2596^2 + 3834^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438779) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 178 + ... + 6550.

Almost surely, 2^21438772 is an apocalyptic number.

It is an amenable number.

21438772 is a deficient number, since it is larger than the sum of its proper divisors (17423506).

21438772 is a wasteful number, since it uses less digits than its factorization.

21438772 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6435 (or 6404 counting only the distinct ones).

The product of its digits is 18816, while the sum is 34.

The square root of 21438772 is about 4630.2021554140. The cubic root of 21438772 is about 277.8006783372.

The spelling of 21438772 in words is "twenty-one million, four hundred thirty-eight thousand, seven hundred seventy-two".