21608717 has 8 divisors (see below), whose sum is σ = 24640056. Its totient is φ = 18772992.

The previous prime is 21608711. The next prime is 21608749. The reversal of 21608717 is 71780612.

It can be written as a sum of positive squares in 4 ways, for example, as 988036 + 20620681 = 994^2 + 4541^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21608717 - 2¹² = 21604621 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 (21608711) 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, 48668 + ... + 49109.

It is an arithmetic number, because the mean of its divisors is an integer number (3080007).

Almost surely, 2^21608717 is an apocalyptic number.

It is an amenable number.

21608717 is a deficient number, since it is larger than the sum of its proper divisors (3031339).

21608717 is a wasteful number, since it uses less digits than its factorization.

21608717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97807.

The product of its (nonzero) digits is 4704, while the sum is 32.

The square root of 21608717 is about 4648.5177207364. The cubic root of 21608717 is about 278.5327886170.

The spelling of 21608717 in words is "twenty-one million, six hundred eight thousand, seven hundred seventeen".