21368717 has 4 divisors (see below), whose sum is σ = 21393696. Its totient is φ = 21343740.

The previous prime is 21368713. The next prime is 21368723. The reversal of 21368717 is 71786312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21368717 - 2² = 21368713 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 (21368713) 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, 11159 + ... + 12932.

It is an arithmetic number, because the mean of its divisors is an integer number (5348424).

Almost surely, 2^21368717 is an apocalyptic number.

It is an amenable number.

21368717 is a deficient number, since it is larger than the sum of its proper divisors (24979).

21368717 is an equidigital number, since it uses as much as digits as its factorization.

21368717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24978.

The product of its digits is 14112, while the sum is 35.

The square root of 21368717 is about 4622.6309608274. The cubic root of 21368717 is about 277.4977604451.

The spelling of 21368717 in words is "twenty-one million, three hundred sixty-eight thousand, seven hundred seventeen".