21951931 has 2 divisors, whose sum is σ = 21951932. Its totient is φ = 21951930.

The previous prime is 21951929. The next prime is 21951971. The reversal of 21951931 is 13915912.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21951931 - 2¹ = 21951929 is a prime.

It is a super-2 number, since 2×21951931² = 963774549257522, which contains 22 as substring.

Together with 21951929, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21951893 and 21951902.

It is not a weakly prime, because it can be changed into another prime (21951971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10975965 + 10975966.

It is an arithmetic number, because the mean of its divisors is an integer number (10975966).

Almost surely, 2^21951931 is an apocalyptic number.

21951931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21951931 is an equidigital number, since it uses as much as digits as its factorization.

21951931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2430, while the sum is 31.

The square root of 21951931 is about 4685.2887851231. The cubic root of 21951931 is about 279.9997066323. Note that the first 3 decimals are identical.

The spelling of 21951931 in words is "twenty-one million, nine hundred fifty-one thousand, nine hundred thirty-one".