21086971 has 2 divisors, whose sum is σ = 21086972. Its totient is φ = 21086970.

The previous prime is 21086963. The next prime is 21086981. The reversal of 21086971 is 17968012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21086971 - 2³ = 21086963 is a prime.

It is not a weakly prime, because it can be changed into another prime (21086911) 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, 10543485 + 10543486.

It is an arithmetic number, because the mean of its divisors is an integer number (10543486).

Almost surely, 2^21086971 is an apocalyptic number.

21086971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21086971 is an equidigital number, since it uses as much as digits as its factorization.

21086971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21086971 is about 4592.0552043720. The cubic root of 21086971 is about 276.2727603532.

The spelling of 21086971 in words is "twenty-one million, eighty-six thousand, nine hundred seventy-one".