21937817 has 4 divisors (see below), whose sum is σ = 23932176. Its totient is φ = 19943460.

The previous prime is 21937807. The next prime is 21937819. The reversal of 21937817 is 71873912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21937817 - 2⁶ = 21937753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21937819) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 997163 + ... + 997184.

It is an arithmetic number, because the mean of its divisors is an integer number (5983044).

Almost surely, 2^21937817 is an apocalyptic number.

It is an amenable number.

21937817 is a deficient number, since it is larger than the sum of its proper divisors (1994359).

21937817 is a wasteful number, since it uses less digits than its factorization.

21937817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1994358.

The product of its digits is 21168, while the sum is 38.

The square root of 21937817 is about 4683.7823390931. The cubic root of 21937817 is about 279.9396851377.

The spelling of 21937817 in words is "twenty-one million, nine hundred thirty-seven thousand, eight hundred seventeen".