21725720 has 16 divisors (see below), whose sum is σ = 48882960. Its totient is φ = 8690272.

The previous prime is 21725689. The next prime is 21725773. The reversal of 21725720 is 2752712.

It is a self number, because there is not a number n which added to its sum of digits gives 21725720.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271532 + ... + 271611.

It is an arithmetic number, because the mean of its divisors is an integer number (3055185).

Almost surely, 2^21725720 is an apocalyptic number.

21725720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21725720 is an abundant number, since it is smaller than the sum of its proper divisors (27157240).

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

21725720 is a wasteful number, since it uses less digits than its factorization.

21725720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 543154 (or 543150 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 26.

The square root of 21725720 is about 4661.0857104327. The cubic root of 21725720 is about 279.0346004373.

The spelling of 21725720 in words is "twenty-one million, seven hundred twenty-five thousand, seven hundred twenty".