21715191 has 6 divisors (see below), whose sum is σ = 31366400. Its totient is φ = 14476788.

The previous prime is 21715153. The next prime is 21715217. The reversal of 21715191 is 19151712.

It is not a de Polignac number, because 21715191 - 2⁷ = 21715063 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21715891) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1206391 + ... + 1206408.

Almost surely, 2^21715191 is an apocalyptic number.

21715191 is a deficient number, since it is larger than the sum of its proper divisors (9651209).

21715191 is a wasteful number, since it uses less digits than its factorization.

21715191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2412805 (or 2412802 counting only the distinct ones).

The product of its digits is 630, while the sum is 27.

The square root of 21715191 is about 4659.9561156732. The cubic root of 21715191 is about 278.9895166986.

The spelling of 21715191 in words is "twenty-one million, seven hundred fifteen thousand, one hundred ninety-one".