21986231 has 2 divisors, whose sum is σ = 21986232. Its totient is φ = 21986230.

The previous prime is 21986227. The next prime is 21986233. The reversal of 21986231 is 13268912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21986231 - 2² = 21986227 is a prime.

It is a super-2 number, since 2×21986231² = 966788707170722, which contains 22 as substring.

Together with 21986233, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21986233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10993115 + 10993116.

It is an arithmetic number, because the mean of its divisors is an integer number (10993116).

Almost surely, 2^21986231 is an apocalyptic number.

21986231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21986231 is an equidigital number, since it uses as much as digits as its factorization.

21986231 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 32.

The square root of 21986231 is about 4688.9477497622. The cubic root of 21986231 is about 280.1454643819.

The spelling of 21986231 in words is "twenty-one million, nine hundred eighty-six thousand, two hundred thirty-one".