21715873 has 2 divisors, whose sum is σ = 21715874. Its totient is φ = 21715872.

The previous prime is 21715861. The next prime is 21715891. The reversal of 21715873 is 37851712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21687649 + 28224 = 4657^2 + 168^2 .

It is a cyclic number.

It is not a de Polignac number, because 21715873 - 2⁹ = 21715361 is a prime.

It is not a weakly prime, because it can be changed into another prime (21715823) 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, 10857936 + 10857937.

It is an arithmetic number, because the mean of its divisors is an integer number (10857937).

Almost surely, 2^21715873 is an apocalyptic number.

It is an amenable number.

21715873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21715873 is an equidigital number, since it uses as much as digits as its factorization.

21715873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11760, while the sum is 34.

The square root of 21715873 is about 4660.0292917534. The cubic root of 21715873 is about 278.9924373707.

The spelling of 21715873 in words is "twenty-one million, seven hundred fifteen thousand, eight hundred seventy-three".