21252431 has 12 divisors (see below), whose sum is σ = 23756112. Its totient is φ = 18944064.

The previous prime is 21252403. The next prime is 21252433. The reversal of 21252431 is 13425212.

It is not a de Polignac number, because 21252431 - 2⁶ = 21252367 is a prime.

It is a super-2 number, since 2×21252431² = 903331646819522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252433) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4406 + ... + 7868.

It is an arithmetic number, because the mean of its divisors is an integer number (1979676).

Almost surely, 2^21252431 is an apocalyptic number.

21252431 is a deficient number, since it is larger than the sum of its proper divisors (2503681).

21252431 is a wasteful number, since it uses less digits than its factorization.

21252431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3518 (or 3499 counting only the distinct ones).

The product of its digits is 480, while the sum is 20.

The square root of 21252431 is about 4610.0359000771. The cubic root of 21252431 is about 276.9934747167.

Adding to 21252431 its reverse (13425212), we get a palindrome (34677643).

The spelling of 21252431 in words is "twenty-one million, two hundred fifty-two thousand, four hundred thirty-one".