21679718765 has 8 divisors (see below), whose sum is σ = 26718788760. Its totient is φ = 16875024192.

The previous prime is 21679718747. The next prime is 21679718803. The reversal of 21679718765 is 56781797612.

It can be written as a sum of positive squares in 4 ways, for example, as 2553381961 + 19126336804 = 50531^2 + 138298^2 .

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 21679718765 - 2¹⁸ = 21679456621 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58593650 + ... + 58594019.

It is an arithmetic number, because the mean of its divisors is an integer number (3339848595).

Almost surely, 2^21679718765 is an apocalyptic number.

It is an amenable number.

21679718765 is a deficient number, since it is larger than the sum of its proper divisors (5039069995).

21679718765 is a wasteful number, since it uses less digits than its factorization.

21679718765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117187711.

The product of its digits is 8890560, while the sum is 59.

The spelling of 21679718765 in words is "twenty-one billion, six hundred seventy-nine million, seven hundred eighteen thousand, seven hundred sixty-five".