21957321 has 8 divisors (see below), whose sum is σ = 30286080. Its totient is φ = 14133392.

The previous prime is 21957311. The next prime is 21957323. The reversal of 21957321 is 12375912.

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 21957321 - 2⁵ = 21957289 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21957323) 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, 126105 + ... + 126278.

It is an arithmetic number, because the mean of its divisors is an integer number (3785760).

Almost surely, 2^21957321 is an apocalyptic number.

It is an amenable number.

21957321 is a deficient number, since it is larger than the sum of its proper divisors (8328759).

21957321 is a wasteful number, since it uses less digits than its factorization.

21957321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 252415.

The product of its digits is 3780, while the sum is 30.

The square root of 21957321 is about 4685.8639544912. The cubic root of 21957321 is about 280.0226214717.

The spelling of 21957321 in words is "twenty-one million, nine hundred fifty-seven thousand, three hundred twenty-one".