21381937 has 8 divisors (see below), whose sum is σ = 22734432. Its totient is φ = 20040000.

The previous prime is 21381931. The next prime is 21381977. The reversal of 21381937 is 73918312.

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

It is a cyclic number.

It is not a de Polignac number, because 21381937 - 2³ = 21381929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21381931) 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, 1762 + ... + 6772.

It is an arithmetic number, because the mean of its divisors is an integer number (2841804).

Almost surely, 2^21381937 is an apocalyptic number.

It is an amenable number.

21381937 is a deficient number, since it is larger than the sum of its proper divisors (1352495).

21381937 is a wasteful number, since it uses less digits than its factorization.

21381937 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5279.

The product of its digits is 9072, while the sum is 34.

The square root of 21381937 is about 4624.0606613668. The cubic root of 21381937 is about 277.5549743641.

Subtracting 21381937 from its reverse (73918312), we obtain a triangular number (52536375 = T₁₀₂₅₀).

The spelling of 21381937 in words is "twenty-one million, three hundred eighty-one thousand, nine hundred thirty-seven".