21955831 has 2 divisors, whose sum is σ = 21955832. Its totient is φ = 21955830.

The previous prime is 21955807. The next prime is 21955841. The reversal of 21955831 is 13855912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21955831 - 2⁵ = 21955799 is a prime.

It is a super-2 number, since 2×21955831² = 964117029801122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21955841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10977915 + 10977916.

It is an arithmetic number, because the mean of its divisors is an integer number (10977916).

Almost surely, 2^21955831 is an apocalyptic number.

21955831 is the 2964-th centered pentagonal number.

21955831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21955831 is an equidigital number, since it uses as much as digits as its factorization.

21955831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 34.

The square root of 21955831 is about 4685.7049629698. The cubic root of 21955831 is about 280.0162873179.

The spelling of 21955831 in words is "twenty-one million, nine hundred fifty-five thousand, eight hundred thirty-one".