664321720320 has 680 divisors, whose sum is σ = 2414717887296. Its totient is φ = 175432531968.

The previous prime is 664321720297. The next prime is 664321720339. The reversal of 664321720320 is 23027123466.

664321720320 is a `hidden beast` number, since 6 + 6 + 4 + 321 + 7 + 2 + 0 + 320 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 6449725389 + ... + 6449725491.

Almost surely, 2^664321720320 is an apocalyptic number.

664321720320 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 664321720320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1207358943648).

664321720320 is an abundant number, since it is smaller than the sum of its proper divisors (1750396166976).

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

664321720320 is an frugal number, since it uses more digits than its factorization.

664321720320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 36.

Adding to 664321720320 its reverse (23027123466), we get a palindrome (687348843786).

The spelling of 664321720320 in words is "six hundred sixty-four billion, three hundred twenty-one million, seven hundred twenty thousand, three hundred twenty".