21990131 has 2 divisors, whose sum is σ = 21990132. Its totient is φ = 21990130.

The previous prime is 21990113. The next prime is 21990169. The reversal of 21990131 is 13109912.

Together with previous prime (21990113) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21990131 - 2¹⁸ = 21727987 is a prime.

It is a super-2 number, since 2×21990131² = 967131722794322, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21990131.

It is not a weakly prime, because it can be changed into another prime (21990181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10995065 + 10995066.

It is an arithmetic number, because the mean of its divisors is an integer number (10995066).

Almost surely, 2^21990131 is an apocalyptic number.

21990131 is a deficient number, since it is larger than the sum of its proper divisors (1).

21990131 is an equidigital number, since it uses as much as digits as its factorization.

21990131 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 26.

The square root of 21990131 is about 4689.3636028783. The cubic root of 21990131 is about 280.1620278198.

The spelling of 21990131 in words is "twenty-one million, nine hundred ninety thousand, one hundred thirty-one".