666651816 has 64 divisors (see below), whose sum is σ = 1856462400. Its totient is φ = 221659200.

The previous prime is 666651751. The next prime is 666651823. The reversal of 666651816 is 618156666.

666651816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87271 + ... + 94601.

It is an arithmetic number, because the mean of its divisors is an integer number (29007225).

Almost surely, 2^666651816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666651816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (928231200).

666651816 is an abundant number, since it is smaller than the sum of its proper divisors (1189810584).

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

666651816 is a wasteful number, since it uses less digits than its factorization.

666651816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7767 (or 7757 counting only the distinct ones).

The product of its digits is 311040, while the sum is 45.

The square root of 666651816 is about 25819.6013911912. The cubic root of 666651816 is about 873.5739780620.

The spelling of 666651816 in words is "six hundred sixty-six million, six hundred fifty-one thousand, eight hundred sixteen".