21937187 has 2 divisors, whose sum is σ = 21937188. Its totient is φ = 21937186.

The previous prime is 21937171. The next prime is 21937213. The reversal of 21937187 is 78173912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21937187 - 2⁴ = 21937171 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21937187.

It is not a weakly prime, because it can be changed into another prime (21937117) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10968593 + 10968594.

It is an arithmetic number, because the mean of its divisors is an integer number (10968594).

Almost surely, 2^21937187 is an apocalyptic number.

21937187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21937187 is an equidigital number, since it uses as much as digits as its factorization.

21937187 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21937187 is about 4683.7150852715. The cubic root of 21937187 is about 279.9370053863.

The spelling of 21937187 in words is "twenty-one million, nine hundred thirty-seven thousand, one hundred eighty-seven".