21715723 has 2 divisors, whose sum is σ = 21715724. Its totient is φ = 21715722.

The previous prime is 21715721. The next prime is 21715741. The reversal of 21715723 is 32751712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21715723 - 2¹ = 21715721 is a prime.

Together with 21715721, it forms a pair of twin primes.

It is equal to p_1372375 and since 21715723 and 1372375 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21715691 and 21715700.

It is not a weakly prime, because it can be changed into another prime (21715721) 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, 10857861 + 10857862.

It is an arithmetic number, because the mean of its divisors is an integer number (10857862).

Almost surely, 2^21715723 is an apocalyptic number.

21715723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21715723 is an equidigital number, since it uses as much as digits as its factorization.

21715723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2940, while the sum is 28.

The square root of 21715723 is about 4660.0131974062. The cubic root of 21715723 is about 278.9917949994.

The spelling of 21715723 in words is "twenty-one million, seven hundred fifteen thousand, seven hundred twenty-three".