668907720 has 160 divisors (see below), whose sum is σ = 2421369720. Its totient is φ = 164643840.

The previous prime is 668907691. The next prime is 668907737. The reversal of 668907720 is 27709866.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 570540996 + 98366724 = 23886^2 + 9918^2 .

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 (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 34180 + ... + 50060.

Almost surely, 2^668907720 is an apocalyptic number.

668907720 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 668907720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1210684860).

668907720 is an abundant number, since it is smaller than the sum of its proper divisors (1752462000).

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

668907720 is a wasteful number, since it uses less digits than its factorization.

668907720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15917 (or 15904 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 45.

The square root of 668907720 is about 25863.2503757745. The cubic root of 668907720 is about 874.5582401362.

The spelling of 668907720 in words is "six hundred sixty-eight million, nine hundred seven thousand, seven hundred twenty".