21975621 has 8 divisors (see below), whose sum is σ = 30246144. Its totient is φ = 14177760.

The previous prime is 21975601. The next prime is 21975637. The reversal of 21975621 is 12657912.

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

It is a de Polignac number, because none of the positive numbers 2^k-21975621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21975601) 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, 118056 + ... + 118241.

It is an arithmetic number, because the mean of its divisors is an integer number (3780768).

Almost surely, 2^21975621 is an apocalyptic number.

It is an amenable number.

21975621 is a deficient number, since it is larger than the sum of its proper divisors (8270523).

21975621 is a wasteful number, since it uses less digits than its factorization.

21975621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236331.

The product of its digits is 7560, while the sum is 33.

The square root of 21975621 is about 4687.8162293332. The cubic root of 21975621 is about 280.1003934216.

The spelling of 21975621 in words is "twenty-one million, nine hundred seventy-five thousand, six hundred twenty-one".