21686685679 has 2 divisors, whose sum is σ = 21686685680. Its totient is φ = 21686685678.

The previous prime is 21686685659. The next prime is 21686685701. The reversal of 21686685679 is 97658668612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21686685679 - 2¹⁹ = 21686161391 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21686685679.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21686685649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10843342839 + 10843342840.

It is an arithmetic number, because the mean of its divisors is an integer number (10843342840).

Almost surely, 2^21686685679 is an apocalyptic number.

21686685679 is a deficient number, since it is larger than the sum of its proper divisors (1).

21686685679 is an equidigital number, since it uses as much as digits as its factorization.

21686685679 is an evil number, because the sum of its binary digits is even.

The product of its digits is 52254720, while the sum is 64.

The spelling of 21686685679 in words is "twenty-one billion, six hundred eighty-six million, six hundred eighty-five thousand, six hundred seventy-nine".