21957637 has 4 divisors (see below), whose sum is σ = 23646700. Its totient is φ = 20268576.

The previous prime is 21957631. The next prime is 21957671. The reversal of 21957637 is 73675912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10458756 + 11498881 = 3234^2 + 3391^2 .

It is a cyclic number.

It is not a de Polignac number, because 21957637 - 2³ = 21957629 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21957637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21957631) 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, 844512 + ... + 844537.

It is an arithmetic number, because the mean of its divisors is an integer number (5911675).

Almost surely, 2^21957637 is an apocalyptic number.

It is an amenable number.

21957637 is a deficient number, since it is larger than the sum of its proper divisors (1689063).

21957637 is a wasteful number, since it uses less digits than its factorization.

21957637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1689062.

The product of its digits is 79380, while the sum is 40.

The square root of 21957637 is about 4685.8976728051. The cubic root of 21957637 is about 280.0239647856.

The spelling of 21957637 in words is "twenty-one million, nine hundred fifty-seven thousand, six hundred thirty-seven".