668388653856 has 672 divisors, whose sum is σ = 2471864024448. Its totient is φ = 172754104320.

The previous prime is 668388653813. The next prime is 668388653887. The reversal of 668388653856 is 658356883866.

668388653856 is a `hidden beast` number, since 6 + 6 + 8 + 3 + 8 + 86 + 538 + 5 + 6 = 666.

668388653856 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (672).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is an unprimeable number.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 418526850 + ... + 418528446.

It is an arithmetic number, because the mean of its divisors is an integer number (3678369084).

Almost surely, 2^668388653856 is an apocalyptic number.

668388653856 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 668388653856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1235932012224).

668388653856 is an abundant number, since it is smaller than the sum of its proper divisors (1803475370592).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

668388653856 is a wasteful number, since it uses less digits than its factorization.

668388653856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1876 (or 1853 counting only the distinct ones).

The product of its digits is 1194393600, while the sum is 72.

The spelling of 668388653856 in words is "six hundred sixty-eight billion, three hundred eighty-eight million, six hundred fifty-three thousand, eight hundred fifty-six".