21957831 has 32 divisors (see below), whose sum is σ = 37952000. Its totient is φ = 12542040.

The previous prime is 21957811. The next prime is 21957841. The reversal of 21957831 is 13875912.

It is not a de Polignac number, because 21957831 - 2⁵ = 21957799 is a prime.

It is a super-2 number, since 2×21957831² = 964292684449122, 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 (21957811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8076 + ... + 10446.

It is an arithmetic number, because the mean of its divisors is an integer number (1186000).

Almost surely, 2^21957831 is an apocalyptic number.

21957831 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21957831 is a deficient number, since it is larger than the sum of its proper divisors (15994169).

21957831 is an equidigital number, since it uses as much as digits as its factorization.

21957831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2401 (or 2381 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21957831 is about 4685.9183731687. The cubic root of 21957831 is about 280.0247894719.

The spelling of 21957831 in words is "twenty-one million, nine hundred fifty-seven thousand, eight hundred thirty-one".