668421720 has 80 divisors (see below), whose sum is σ = 2246650560. Its totient is φ = 178244928.

The previous prime is 668421707. The next prime is 668421749. The reversal of 668421720 is 27124866.

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

It is a congruent number.

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 19 ways as a sum of consecutive naturals, for example, 99912 + ... + 106391.

It is an arithmetic number, because the mean of its divisors is an integer number (28083132).

Almost surely, 2^668421720 is an apocalyptic number.

668421720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

668421720 is an abundant number, since it is smaller than the sum of its proper divisors (1578228840).

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

668421720 is a wasteful number, since it uses less digits than its factorization.

668421720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206326 (or 206313 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The square root of 668421720 is about 25853.8530977493. The cubic root of 668421720 is about 874.3463831684.

The spelling of 668421720 in words is "six hundred sixty-eight million, four hundred twenty-one thousand, seven hundred twenty".