21937391 has 16 divisors (see below), whose sum is σ = 25850880. Its totient is φ = 18227040.

The previous prime is 21937387. The next prime is 21937393. The reversal of 21937391 is 19373912.

It is a cyclic number.

It is not a de Polignac number, because 21937391 - 2² = 21937387 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21937393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42845 + ... + 43353.

It is an arithmetic number, because the mean of its divisors is an integer number (1615680).

Almost surely, 2^21937391 is an apocalyptic number.

21937391 is a deficient number, since it is larger than the sum of its proper divisors (3913489).

21937391 is a wasteful number, since it uses less digits than its factorization.

21937391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 694.

The product of its digits is 10206, while the sum is 35.

The square root of 21937391 is about 4683.7368628052. The cubic root of 21937391 is about 279.9378731210.

The spelling of 21937391 in words is "twenty-one million, nine hundred thirty-seven thousand, three hundred ninety-one".