21731172 has 12 divisors (see below), whose sum is σ = 50706096. Its totient is φ = 7243720.

The previous prime is 21731161. The next prime is 21731191. The reversal of 21731172 is 27113712.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 905454 + ... + 905477.

It is an arithmetic number, because the mean of its divisors is an integer number (4225508).

Almost surely, 2^21731172 is an apocalyptic number.

It is an amenable number.

21731172 is an abundant number, since it is smaller than the sum of its proper divisors (28974924).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21731172 is a wasteful number, since it uses less digits than its factorization.

21731172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1810938 (or 1810936 counting only the distinct ones).

The product of its digits is 588, while the sum is 24.

The square root of 21731172 is about 4661.6705160275. The cubic root of 21731172 is about 279.0579394322.

Adding to 21731172 its reverse (27113712), we get a palindrome (48844884).

The spelling of 21731172 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred seventy-two".