20688935696639 has 4 divisors (see below), whose sum is σ = 23644497939024. Its totient is φ = 17733373454256.

The previous prime is 20688935696579. The next prime is 20688935696641. The reversal of 20688935696639 is 93669653988602.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20688935696639 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 (20688935696239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1477781121182 + ... + 1477781121195.

It is an arithmetic number, because the mean of its divisors is an integer number (5911124484756).

Almost surely, 2^{20688935696639} is an apocalyptic number.

20688935696639 is a deficient number, since it is larger than the sum of its proper divisors (2955562242385).

20688935696639 is an equidigital number, since it uses as much as digits as its factorization.

20688935696639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2955562242384.

The product of its (nonzero) digits is 5441955840, while the sum is 80.

The spelling of 20688935696639 in words is "twenty trillion, six hundred eighty-eight billion, nine hundred thirty-five million, six hundred ninety-six thousand, six hundred thirty-nine".