18516868691 has 4 divisors (see below), whose sum is σ = 18518649912. Its totient is φ = 18515087472.

The previous prime is 18516868687. The next prime is 18516868751. The reversal of 18516868691 is 19686861581.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 18516868691 - 2² = 18516868687 is a prime.

It is a super-2 number, since 2×18516868691² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18516868691.

It is not an unprimeable number, because it can be changed into a prime (18516868621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 874925 + ... + 895838.

It is an arithmetic number, because the mean of its divisors is an integer number (4629662478).

Almost surely, 2^18516868691 is an apocalyptic number.

18516868691 is a deficient number, since it is larger than the sum of its proper divisors (1781221).

18516868691 is a wasteful number, since it uses less digits than its factorization.

18516868691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1781220.

The product of its digits is 4976640, while the sum is 59.

The spelling of 18516868691 in words is "eighteen billion, five hundred sixteen million, eight hundred sixty-eight thousand, six hundred ninety-one".