666840720 has 320 divisors, whose sum is σ = 2679828480. Its totient is φ = 133208064.

The previous prime is 666840673. The next prime is 666840731. The reversal of 666840720 is 27048666.

It is a Harshad number since it is a multiple of its sum of digits (39).

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 63 ways as a sum of consecutive naturals, for example, 414157 + ... + 415763.

It is an arithmetic number, because the mean of its divisors is an integer number (8374464).

Almost surely, 2^666840720 is an apocalyptic number.

666840720 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 666840720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1339914240).

666840720 is an abundant number, since it is smaller than the sum of its proper divisors (2012987760).

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

666840720 is a wasteful number, since it uses less digits than its factorization.

666840720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1662 (or 1656 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 39.

The square root of 666840720 is about 25823.2592830572. The cubic root of 666840720 is about 873.6564829170.

The spelling of 666840720 in words is "six hundred sixty-six million, eight hundred forty thousand, seven hundred twenty".