21724672 has 40 divisors (see below), whose sum is σ = 43849872. Its totient is φ = 10752000.

The previous prime is 21724663. The next prime is 21724721. The reversal of 21724672 is 27642712.

It is a super-2 number, since 2×21724672² = 943922747015168, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77172 + ... + 77452.

Almost surely, 2^21724672 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21724672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21924936).

21724672 is an abundant number, since it is smaller than the sum of its proper divisors (22125200).

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

21724672 is an equidigital number, since it uses as much as digits as its factorization.

21724672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 450 (or 434 counting only the distinct ones).

The product of its digits is 9408, while the sum is 31.

The square root of 21724672 is about 4660.9732889172. The cubic root of 21724672 is about 279.0301136974.

The spelling of 21724672 in words is "twenty-one million, seven hundred twenty-four thousand, six hundred seventy-two".