666770778 has 20 divisors (see below), whose sum is σ = 1494060810. Its totient is φ = 222256872.

The previous prime is 666770749. The next prime is 666770807. The reversal of 666770778 is 877077666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (666770749) and next prime (666770807).

It can be written as a sum of positive squares in only one way, i.e., 663938289 + 2832489 = 25767^2 + 1683^2 .

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 2057773 + ... + 2058096.

Almost surely, 2^666770778 is an apocalyptic number.

666770778 is an abundant number, since it is smaller than the sum of its proper divisors (827290032).

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

666770778 is a wasteful number, since it uses less digits than its factorization.

666770778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4115883 (or 4115874 counting only the distinct ones).

The product of its (nonzero) digits is 4148928, while the sum is 54.

The square root of 666770778 is about 25821.9050033107. The cubic root of 666770778 is about 873.6259371828.

The spelling of 666770778 in words is "six hundred sixty-six million, seven hundred seventy thousand, seven hundred seventy-eight".