21088717 has 4 divisors (see below), whose sum is σ = 22710940. Its totient is φ = 19466496.

The previous prime is 21088703. The next prime is 21088741. The reversal of 21088717 is 71788012.

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 13586596 + 7502121 = 3686^2 + 2739^2 .

It is a cyclic number.

It is not a de Polignac number, because 21088717 - 2⁷ = 21088589 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 (21088747) 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, 811092 + ... + 811117.

It is an arithmetic number, because the mean of its divisors is an integer number (5677735).

Almost surely, 2^21088717 is an apocalyptic number.

It is an amenable number.

21088717 is a deficient number, since it is larger than the sum of its proper divisors (1622223).

21088717 is a wasteful number, since it uses less digits than its factorization.

21088717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1622222.

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 21088717 is about 4592.2453113918. The cubic root of 21088717 is about 276.2803852657.

The spelling of 21088717 in words is "twenty-one million, eighty-eight thousand, seven hundred seventeen".