21768717 has 8 divisors (see below), whose sum is σ = 29291680. Its totient is φ = 14379120.

The previous prime is 21768709. The next prime is 21768731. The reversal of 21768717 is 71786712.

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

It is not a de Polignac number, because 21768717 - 2³ = 21768709 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 (21768757) 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, 32959 + ... + 33612.

It is an arithmetic number, because the mean of its divisors is an integer number (3661460).

Almost surely, 2^21768717 is an apocalyptic number.

It is an amenable number.

21768717 is a deficient number, since it is larger than the sum of its proper divisors (7522963).

21768717 is a wasteful number, since it uses less digits than its factorization.

21768717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66683.

The product of its digits is 32928, while the sum is 39.

The square root of 21768717 is about 4665.6957680500. The cubic root of 21768717 is about 279.2185566671.

The spelling of 21768717 in words is "twenty-one million, seven hundred sixty-eight thousand, seven hundred seventeen".