21725621 has 8 divisors (see below), whose sum is σ = 22565664. Its totient is φ = 20900880.

The previous prime is 21725617. The next prime is 21725633. The reversal of 21725621 is 12652712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21725621 - 2² = 21725617 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21725651) 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, 890 + ... + 6651.

It is an arithmetic number, because the mean of its divisors is an integer number (2820708).

Almost surely, 2^21725621 is an apocalyptic number.

It is an amenable number.

21725621 is a deficient number, since it is larger than the sum of its proper divisors (840043).

21725621 is an equidigital number, since it uses as much as digits as its factorization.

21725621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7651.

The product of its digits is 1680, while the sum is 26.

The square root of 21725621 is about 4661.0750905773. The cubic root of 21725621 is about 279.0341766006.

The spelling of 21725621 in words is "twenty-one million, seven hundred twenty-five thousand, six hundred twenty-one".