21866231 has 4 divisors (see below), whose sum is σ = 22374792. Its totient is φ = 21357672.

The previous prime is 21866219. The next prime is 21866239. The reversal of 21866231 is 13266812.

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-21866231 is a prime.

It is a super-2 number, since 2×21866231² = 956264116290722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21866194 and 21866203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21866239) 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, 254216 + ... + 254301.

It is an arithmetic number, because the mean of its divisors is an integer number (5593698).

Almost surely, 2^21866231 is an apocalyptic number.

21866231 is a deficient number, since it is larger than the sum of its proper divisors (508561).

21866231 is an equidigital number, since it uses as much as digits as its factorization.

21866231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 508560.

The product of its digits is 3456, while the sum is 29.

The square root of 21866231 is about 4676.1341939683. The cubic root of 21866231 is about 279.6348599225.

The spelling of 21866231 in words is "twenty-one million, eight hundred sixty-six thousand, two hundred thirty-one".