21868717 has 6 divisors (see below), whose sum is σ = 23569098. Its totient is φ = 20170944.

The previous prime is 21868709. The next prime is 21868723. The reversal of 21868717 is 71786812.

It can be written as a sum of positive squares in 3 ways, for example, as 13995081 + 7873636 = 3741^2 + 2806^2 .

It is not a de Polignac number, because 21868717 - 2³ = 21868709 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21868717.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21868787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 16213 + ... + 17509.

It is an arithmetic number, because the mean of its divisors is an integer number (3928183).

Almost surely, 2^21868717 is an apocalyptic number.

It is an amenable number.

21868717 is a deficient number, since it is larger than the sum of its proper divisors (1700381).

21868717 is an frugal number, since it uses more digits than its factorization.

21868717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2607 (or 1310 counting only the distinct ones).

The product of its digits is 37632, while the sum is 40.

The square root of 21868717 is about 4676.4000042768. The cubic root of 21868717 is about 279.6454568702.

The spelling of 21868717 in words is "twenty-one million, eight hundred sixty-eight thousand, seven hundred seventeen".