21931384 has 32 divisors (see below), whose sum is σ = 42762240. Its totient is φ = 10533600.

The previous prime is 21931369. The next prime is 21931387. The reversal of 21931384 is 48313912.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21931387) 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 in 7 ways as a sum of consecutive naturals, for example, 47137 + ... + 47599.

It is an arithmetic number, because the mean of its divisors is an integer number (1336320).

Almost surely, 2^21931384 is an apocalyptic number.

It is an amenable number.

21931384 is a deficient number, since it is larger than the sum of its proper divisors (20830856).

21931384 is a wasteful number, since it uses less digits than its factorization.

21931384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 691 (or 687 counting only the distinct ones).

The product of its digits is 5184, while the sum is 31.

The square root of 21931384 is about 4683.0955574278. The cubic root of 21931384 is about 279.9123194850.

The spelling of 21931384 in words is "twenty-one million, nine hundred thirty-one thousand, three hundred eighty-four".