21641831 has 2 divisors, whose sum is σ = 21641832. Its totient is φ = 21641830.

The previous prime is 21641797. The next prime is 21641843. The reversal of 21641831 is 13814612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21641831 is a prime.

It is a super-2 number, since 2×21641831² = 936737698065122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21641831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21641231) 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 as a sum of consecutive naturals, namely, 10820915 + 10820916.

It is an arithmetic number, because the mean of its divisors is an integer number (10820916).

Almost surely, 2^21641831 is an apocalyptic number.

21641831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21641831 is an equidigital number, since it uses as much as digits as its factorization.

21641831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1152, while the sum is 26.

The square root of 21641831 is about 4652.0781377789. The cubic root of 21641831 is about 278.6749939960.

The spelling of 21641831 in words is "twenty-one million, six hundred forty-one thousand, eight hundred thirty-one".