666660 has 48 divisors (see below), whose sum is σ = 1919232. Its totient is φ = 172800.

The previous prime is 666649. The next prime is 666667. The reversal of 666660 is 66666.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a nialpdrome in base 7 and base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666667) 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 15 ways as a sum of consecutive naturals, for example, 2325 + ... + 2595.

It is an arithmetic number, because the mean of its divisors is an integer number (39984).

2⁶⁶⁶⁶⁶⁰ is an apocalyptic number.

666660 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 666660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (959616).

666660 is an abundant number, since it is smaller than the sum of its proper divisors (1252572).

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

666660 is a wasteful number, since it uses less digits than its factorization.

666660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324 (or 322 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 30.

The square root of 666660 is about 816.4924984346. The cubic root of 666660 is about 87.3577552792.

666660 divided by its sum of digits (30) gives a palindrome (22222).

It can be divided in two parts, 666 and 660, that added together give a triangular number (1326 = T₅₁).

The spelling of 666660 in words is "six hundred sixty-six thousand, six hundred sixty".