21724938 has 12 divisors (see below), whose sum is σ = 47070738. Its totient is φ = 7241640.

The previous prime is 21724931. The next prime is 21724939. The reversal of 21724938 is 83942712.

It can be written as a sum of positive squares in only one way, i.e., 21650409 + 74529 = 4653^2 + 273^2 .

It is a super-2 number, since 2×21724938² = 943945862207688, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21724931) 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, 603453 + ... + 603488.

Almost surely, 2^21724938 is an apocalyptic number.

21724938 is an abundant number, since it is smaller than the sum of its proper divisors (25345800).

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

21724938 is a wasteful number, since it uses less digits than its factorization.

21724938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206949 (or 1206946 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21724938 is about 4661.0018236426. The cubic root of 21724938 is about 279.0312525210.

The spelling of 21724938 in words is "twenty-one million, seven hundred twenty-four thousand, nine hundred thirty-eight".