21938831 has 2 divisors, whose sum is σ = 21938832. Its totient is φ = 21938830.

The previous prime is 21938779. The next prime is 21938843. The reversal of 21938831 is 13883912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21938831 - 2¹⁰ = 21937807 is a prime.

It is a super-2 number, since 2×21938831² = 962624611293122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21938791 and 21938800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21938881) 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, 10969415 + 10969416.

It is an arithmetic number, because the mean of its divisors is an integer number (10969416).

Almost surely, 2^21938831 is an apocalyptic number.

21938831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21938831 is an equidigital number, since it uses as much as digits as its factorization.

21938831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 21938831 is about 4683.8905836922. The cubic root of 21938831 is about 279.9439981537.

The spelling of 21938831 in words is "twenty-one million, nine hundred thirty-eight thousand, eight hundred thirty-one".