21323431 has 4 divisors (see below), whose sum is σ = 21435264. Its totient is φ = 21211600.

The previous prime is 21323417. The next prime is 21323441. The reversal of 21323431 is 13432312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21323431 is a prime.

It is a super-2 number, since 2×21323431² = 909377419223522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21323399 and 21323408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21323441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55630 + ... + 56011.

It is an arithmetic number, because the mean of its divisors is an integer number (5358816).

Almost surely, 2^21323431 is an apocalyptic number.

21323431 is a deficient number, since it is larger than the sum of its proper divisors (111833).

21323431 is a wasteful number, since it uses less digits than its factorization.

21323431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111832.

The product of its digits is 432, while the sum is 19.

The square root of 21323431 is about 4617.7300700669. The cubic root of 21323431 is about 277.3015912587.

Adding to 21323431 its reverse (13432312), we get a palindrome (34755743).

The spelling of 21323431 in words is "twenty-one million, three hundred twenty-three thousand, four hundred thirty-one".