666441515664 has 120 divisors (see below), whose sum is σ = 1891374253080. Its totient is φ = 219039399936.

The previous prime is 666441515653. The next prime is 666441515669. The reversal of 666441515664 is 466515144666.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 18403635600 + 648037880064 = 135660^2 + 805008^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 666441515664.

It is not an unprimeable number, because it can be changed into a prime (666441515669) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3034392 + ... + 3246600.

It is an arithmetic number, because the mean of its divisors is an integer number (15761452109).

Almost surely, 2^666441515664 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 666441515664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (945687126540).

666441515664 is an abundant number, since it is smaller than the sum of its proper divisors (1224932737416).

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

666441515664 is a wasteful number, since it uses less digits than its factorization.

666441515664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212529 (or 212520 counting only the distinct ones).

The product of its digits is 12441600, while the sum is 54.

The spelling of 666441515664 in words is "six hundred sixty-six billion, four hundred forty-one million, five hundred fifteen thousand, six hundred sixty-four".