668561217658 has 16 divisors (see below), whose sum is σ = 1019871000000. Its totient is φ = 328604571712.

The previous prime is 668561217647. The next prime is 668561217661. The reversal of 668561217658 is 856712165866.

It is a junction number, because it is equal to n+sod(n) for n = 668561217596 and 668561217605.

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, 4884843 + ... + 5019841.

It is an arithmetic number, because the mean of its divisors is an integer number (63741937500).

Almost surely, 2^668561217658 is an apocalyptic number.

668561217658 is a deficient number, since it is larger than the sum of its proper divisors (351309782342).

668561217658 is a wasteful number, since it uses less digits than its factorization.

668561217658 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177029.

The product of its digits is 29030400, while the sum is 61.

The spelling of 668561217658 in words is "six hundred sixty-eight billion, five hundred sixty-one million, two hundred seventeen thousand, six hundred fifty-eight".