664791660 has 144 divisors (see below), whose sum is σ = 2189730816. Its totient is φ = 162279936.

The previous prime is 664791649. The next prime is 664791689. The reversal of 664791660 is 66197466.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 296062 + ... + 298298.

It is an arithmetic number, because the mean of its divisors is an integer number (15206464).

Almost surely, 2^664791660 is an apocalyptic number.

664791660 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 664791660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1094865408).

664791660 is an abundant number, since it is smaller than the sum of its proper divisors (1524939156).

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

664791660 is a wasteful number, since it uses less digits than its factorization.

664791660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2392 (or 2387 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 664791660 is about 25783.5540606798. The cubic root of 664791660 is about 872.7607111359.

The spelling of 664791660 in words is "six hundred sixty-four million, seven hundred ninety-one thousand, six hundred sixty".