21724380 has 36 divisors (see below), whose sum is σ = 65897832. Its totient is φ = 5793120.

The previous prime is 21724379. The next prime is 21724399. The reversal of 21724380 is 8342712.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 60166 + ... + 60525.

Almost surely, 2^21724380 is an apocalyptic number.

21724380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21724380 is an abundant number, since it is smaller than the sum of its proper divisors (44173452).

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

21724380 is a wasteful number, since it uses less digits than its factorization.

21724380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120706 (or 120701 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21724380 is about 4660.9419648822. The cubic root of 21724380 is about 279.0288635495.

The spelling of 21724380 in words is "twenty-one million, seven hundred twenty-four thousand, three hundred eighty".