21724304 has 40 divisors (see below), whose sum is σ = 49663488. Its totient is φ = 9008640.

The previous prime is 21724303. The next prime is 21724309. The reversal of 21724304 is 40342712.

It is a self number, because there is not a number n which added to its sum of digits gives 21724304.

It is not an unprimeable number, because it can be changed into a prime (21724303) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 344 + ... + 6600.

Almost surely, 2^21724304 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 21724304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24831744).

21724304 is an abundant number, since it is smaller than the sum of its proper divisors (27939184).

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

21724304 is a wasteful number, since it uses less digits than its factorization.

21724304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6303 (or 6297 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21724304 is about 4660.9338120166. The cubic root of 21724304 is about 279.0285381667.

The spelling of 21724304 in words is "twenty-one million, seven hundred twenty-four thousand, three hundred four".