691992788078 has 4 divisors (see below), whose sum is σ = 1037989182120. Its totient is φ = 345996394038.

The previous prime is 691992788051. The next prime is 691992788111. The reversal of 691992788078 is 870887299196.

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

It is a junction number, because it is equal to n+sod(n) for n = 691992787996 and 691992788014.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 172998197018 + ... + 172998197021.

It is an arithmetic number, because the mean of its divisors is an integer number (259497295530).

Almost surely, 2^691992788078 is an apocalyptic number.

691992788078 is a deficient number, since it is larger than the sum of its proper divisors (345996394042).

691992788078 is a wasteful number, since it uses less digits than its factorization.

691992788078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 345996394041.

The product of its (nonzero) digits is 219469824, while the sum is 74.

The spelling of 691992788078 in words is "six hundred ninety-one billion, nine hundred ninety-two million, seven hundred eighty-eight thousand, seventy-eight".