664181668 has 12 divisors (see below), whose sum is σ = 1163355340. Its totient is φ = 331794432.

The previous prime is 664181657. The next prime is 664181699. The reversal of 664181668 is 866181466.

It can be written as a sum of positive squares in 2 ways, for example, as 62853184 + 601328484 = 7928^2 + 24522^2 .

It is a super-2 number, since 2×664181668² = 882274576214524448, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 69021 + ... + 78052.

Almost surely, 2^664181668 is an apocalyptic number.

It is an amenable number.

664181668 is a deficient number, since it is larger than the sum of its proper divisors (499173672).

664181668 is a wasteful number, since it uses less digits than its factorization.

664181668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148206 (or 148204 counting only the distinct ones).

The product of its digits is 331776, while the sum is 46.

The square root of 664181668 is about 25771.7222552161. The cubic root of 664181668 is about 872.4936901540.

It can be divided in two parts, 66418 and 1668, that added together give a palindrome (68086).

The spelling of 664181668 in words is "six hundred sixty-four million, one hundred eighty-one thousand, six hundred sixty-eight".