721666608 has 80 divisors (see below), whose sum is σ = 2072534016. Its totient is φ = 214882560.

The previous prime is 721666597. The next prime is 721666613. The reversal of 721666608 is 806666127.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 721666608.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 691 + ... + 37997.

Almost surely, 2^721666608 is an apocalyptic number.

721666608 is a gapful number since it is divisible by the number (78) 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 721666608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1036267008).

721666608 is an abundant number, since it is smaller than the sum of its proper divisors (1350867408).

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

721666608 is a wasteful number, since it uses less digits than its factorization.

721666608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37362 (or 37356 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 42.

The square root of 721666608 is about 26863.8531860193. The cubic root of 721666608 is about 896.9719668747.

The spelling of 721666608 in words is "seven hundred twenty-one million, six hundred sixty-six thousand, six hundred eight".