21715791 has 8 divisors (see below), whose sum is σ = 28995120. Its totient is φ = 14456832.

The previous prime is 21715777. The next prime is 21715807. The reversal of 21715791 is 19751712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21715791 - 2⁷ = 21715663 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21715711) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2400 + ... + 7013.

It is an arithmetic number, because the mean of its divisors is an integer number (3624390).

Almost surely, 2^21715791 is an apocalyptic number.

21715791 is a deficient number, since it is larger than the sum of its proper divisors (7279329).

21715791 is an equidigital number, since it uses as much as digits as its factorization.

21715791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10185.

The product of its digits is 4410, while the sum is 33.

The square root of 21715791 is about 4660.0204935172. The cubic root of 21715791 is about 278.9920862081.

The spelling of 21715791 in words is "twenty-one million, seven hundred fifteen thousand, seven hundred ninety-one".