664461640 has 32 divisors (see below), whose sum is σ = 1510460280. Its totient is φ = 263043072.

The previous prime is 664461613. The next prime is 664461641. The reversal of 664461640 is 46164466.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 392277636 + 272184004 = 19806^2 + 16498^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 664461640.

It is not an unprimeable number, because it can be changed into a prime (664461641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81747 + ... + 89506.

Almost surely, 2^664461640 is an apocalyptic number.

It is an amenable number.

664461640 is an abundant number, since it is smaller than the sum of its proper divisors (845998640).

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

664461640 is a wasteful number, since it uses less digits than its factorization.

664461640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171361 (or 171357 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 37.

The square root of 664461640 is about 25777.1534502939. The cubic root of 664461640 is about 872.6162668025.

It can be divided in two parts, 66446 and 1640, that added together give a palindrome (68086).

The spelling of 664461640 in words is "six hundred sixty-four million, four hundred sixty-one thousand, six hundred forty".