21415931 has 2 divisors, whose sum is σ = 21415932. Its totient is φ = 21415930.

The previous prime is 21415871. The next prime is 21415969. The reversal of 21415931 is 13951412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21415931 - 2²² = 17221627 is a prime.

It is a super-2 number, since 2×21415931² = 917284201193522, 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 21415931.

It is not a weakly prime, because it can be changed into another prime (21415991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10707965 + 10707966.

It is an arithmetic number, because the mean of its divisors is an integer number (10707966).

Almost surely, 2^21415931 is an apocalyptic number.

21415931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21415931 is an equidigital number, since it uses as much as digits as its factorization.

21415931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 26.

The square root of 21415931 is about 4627.7349751255. The cubic root of 21415931 is about 277.7019864275.

The spelling of 21415931 in words is "twenty-one million, four hundred fifteen thousand, nine hundred thirty-one".