666720 has 72 divisors (see below), whose sum is σ = 2280096. Its totient is φ = 177408.

The previous prime is 666707. The next prime is 666727. The reversal of 666720 is 27666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1209 + ... + 1671.

It is an arithmetic number, because the mean of its divisors is an integer number (31668).

2⁶⁶⁶⁷²⁰ is an apocalyptic number.

666720 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 666720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1140048).

666720 is an abundant number, since it is smaller than the sum of its proper divisors (1613376).

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

666720 is a wasteful number, since it uses less digits than its factorization.

666720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 484 (or 473 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 666720 is about 816.5292401378. The cubic root of 666720 is about 87.3603759594.

It can be divided in two parts, 66 and 6720, that added together give a triangular number (6786 = T₁₁₆).

The spelling of 666720 in words is "six hundred sixty-six thousand, seven hundred twenty".