21653724 has 12 divisors (see below), whose sum is σ = 50525384. Its totient is φ = 7217904.

The previous prime is 21653707. The next prime is 21653729. The reversal of 21653724 is 42735612.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21653691 and 21653700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 902227 + ... + 902250.

Almost surely, 2^21653724 is an apocalyptic number.

It is an amenable number.

21653724 is an abundant number, since it is smaller than the sum of its proper divisors (28871660).

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

21653724 is a wasteful number, since it uses less digits than its factorization.

21653724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1804484 (or 1804482 counting only the distinct ones).

The product of its digits is 10080, while the sum is 30.

The square root of 21653724 is about 4653.3562081577. The cubic root of 21653724 is about 278.7260321111.

The spelling of 21653724 in words is "twenty-one million, six hundred fifty-three thousand, seven hundred twenty-four".