666544500 has 144 divisors (see below), whose sum is σ = 2226670992. Its totient is φ = 167270400.

The previous prime is 666544477. The next prime is 666544507. The reversal of 666544500 is 5445666.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 15069924 + 651474576 = 3882^2 + 25524^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666544507) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 72144 + ... + 80856.

It is an arithmetic number, because the mean of its divisors is an integer number (15462993).

Almost surely, 2^666544500 is an apocalyptic number.

666544500 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 666544500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1113335496).

666544500 is an abundant number, since it is smaller than the sum of its proper divisors (1560126492).

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

666544500 is a wasteful number, since it uses less digits than its factorization.

666544500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8755 (or 8740 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 36.

The square root of 666544500 is about 25817.5231189981. The cubic root of 666544500 is about 873.5271002698.

The spelling of 666544500 in words is "six hundred sixty-six million, five hundred forty-four thousand, five hundred".