20517997 has 4 divisors (see below), whose sum is σ = 21724956. Its totient is φ = 19311040.

The previous prime is 20517989. The next prime is 20518019. The reversal of 20517997 is 79971502.

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 6522916 + 13995081 = 2554^2 + 3741^2 .

It is a cyclic number.

It is not a de Polignac number, because 20517997 - 2³ = 20517989 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 (20517907) 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, 603454 + ... + 603487.

It is an arithmetic number, because the mean of its divisors is an integer number (5431239).

Almost surely, 2^20517997 is an apocalyptic number.

It is an amenable number.

20517997 is a deficient number, since it is larger than the sum of its proper divisors (1206959).

20517997 is a wasteful number, since it uses less digits than its factorization.

20517997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206958.

The product of its (nonzero) digits is 39690, while the sum is 40.

The square root of 20517997 is about 4529.6795692411. The cubic root of 20517997 is about 273.7652499445.

The spelling of 20517997 in words is "twenty million, five hundred seventeen thousand, nine hundred ninety-seven".