665266856778 has 64 divisors (see below), whose sum is σ = 1510868736000. Its totient is φ = 216887449392.

The previous prime is 665266856753. The next prime is 665266856893. The reversal of 665266856778 is 877658662566.

665266856778 is a `hidden beast` number, since 6 + 6 + 52 + 6 + 6 + 8 + 567 + 7 + 8 = 666.

It is a hoax number, since the sum of its digits (72) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3613113 + ... + 3792771.

It is an arithmetic number, because the mean of its divisors is an integer number (23607324000).

Almost surely, 2^665266856778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665266856778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (755434368000).

665266856778 is an abundant number, since it is smaller than the sum of its proper divisors (845601879222).

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

665266856778 is a wasteful number, since it uses less digits than its factorization.

665266856778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181176 (or 181170 counting only the distinct ones).

The product of its digits is 1219276800, while the sum is 72.

The spelling of 665266856778 in words is "six hundred sixty-five billion, two hundred sixty-six million, eight hundred fifty-six thousand, seven hundred seventy-eight".