20715917 has 4 divisors (see below), whose sum is σ = 20855100. Its totient is φ = 20576736.

The previous prime is 20715913. The next prime is 20715923. The reversal of 20715917 is 71951702.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7070281 + 13645636 = 2659^2 + 3694^2 .

It is a cyclic number.

It is not a de Polignac number, because 20715917 - 2² = 20715913 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 (20715913) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 69368 + ... + 69665.

It is an arithmetic number, because the mean of its divisors is an integer number (5213775).

Almost surely, 2^20715917 is an apocalyptic number.

It is an amenable number.

20715917 is a deficient number, since it is larger than the sum of its proper divisors (139183).

20715917 is a wasteful number, since it uses less digits than its factorization.

20715917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139182.

The product of its (nonzero) digits is 4410, while the sum is 32.

The square root of 20715917 is about 4551.4741567980. The cubic root of 20715917 is about 274.6426962919.

The spelling of 20715917 in words is "twenty million, seven hundred fifteen thousand, nine hundred seventeen".