21504231 has 16 divisors (see below), whose sum is σ = 36409600. Its totient is φ = 12288024.

The previous prime is 21504227. The next prime is 21504233. The reversal of 21504231 is 13240512.

It is not a de Polignac number, because 21504231 - 2² = 21504227 is a prime.

It is a super-2 number, since 2×21504231² = 924863901802722, 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 (21504233) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56701 + ... + 57078.

It is an arithmetic number, because the mean of its divisors is an integer number (2275600).

Almost surely, 2^21504231 is an apocalyptic number.

21504231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21504231 is a deficient number, since it is larger than the sum of its proper divisors (14905369).

21504231 is a wasteful number, since it uses less digits than its factorization.

21504231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113795 (or 113789 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21504231 is about 4637.2654657675. The cubic root of 21504231 is about 278.0831273241.

Adding to 21504231 its reverse (13240512), we get a palindrome (34744743).

The spelling of 21504231 in words is "twenty-one million, five hundred four thousand, two hundred thirty-one".