21402971 has 2 divisors, whose sum is σ = 21402972. Its totient is φ = 21402970.

The previous prime is 21402967. The next prime is 21402977. The reversal of 21402971 is 17920412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21402971 - 2² = 21402967 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21402971.

It is not a weakly prime, because it can be changed into another prime (21402977) 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, 10701485 + 10701486.

It is an arithmetic number, because the mean of its divisors is an integer number (10701486).

Almost surely, 2^21402971 is an apocalyptic number.

21402971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21402971 is an equidigital number, since it uses as much as digits as its factorization.

21402971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21402971 is about 4626.3345101711. The cubic root of 21402971 is about 277.6459573592.

The spelling of 21402971 in words is "twenty-one million, four hundred two thousand, nine hundred seventy-one".