21724560 has 240 divisors, whose sum is σ = 86119488. Its totient is φ = 4838400.

The previous prime is 21724553. The next prime is 21724607. The reversal of 21724560 is 6542712.

It is a tau number, because it is divible by the number of its divisors (240).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 102855 + ... + 103065.

Almost surely, 2^21724560 is an apocalyptic number.

21724560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21724560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43059744).

21724560 is an abundant number, since it is smaller than the sum of its proper divisors (64394928).

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

21724560 is a wasteful number, since it uses less digits than its factorization.

21724560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254 (or 245 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21724560 is about 4660.9612742438. The cubic root of 21724560 is about 279.0296341899.

The spelling of 21724560 in words is "twenty-one million, seven hundred twenty-four thousand, five hundred sixty".