21567231 has 12 divisors (see below), whose sum is σ = 35603152. Its totient is φ = 12324096.

The previous prime is 21567229. The next prime is 21567251. The reversal of 21567231 is 13276512.

It is a happy number.

It is not a de Polignac number, because 21567231 - 2¹ = 21567229 is a prime.

It is a super-2 number, since 2×21567231² = 930290906014722, 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 = 21567195 and 21567204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21567251) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 171106 + ... + 171231.

Almost surely, 2^21567231 is an apocalyptic number.

21567231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21567231 is a deficient number, since it is larger than the sum of its proper divisors (14035921).

21567231 is a wasteful number, since it uses less digits than its factorization.

21567231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 342350 (or 342347 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21567231 is about 4644.0532942678. The cubic root of 21567231 is about 278.3544251967.

The spelling of 21567231 in words is "twenty-one million, five hundred sixty-seven thousand, two hundred thirty-one".