666566100 has 162 divisors, whose sum is σ = 2151277674. Its totient is φ = 172627200.

The previous prime is 666566081. The next prime is 666566119. The reversal of 666566100 is 1665666.

It is an interprime number because it is at equal distance from previous prime (666566081) and next prime (666566119).

It can be written as a sum of positive squares in 9 ways, for example, as 11410884 + 655155216 = 3378^2 + 25596^2 .

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 polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 1231830 + ... + 1232370.

Almost surely, 2^666566100 is an apocalyptic number.

666566100 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 666566100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1075638837).

666566100 is an abundant number, since it is smaller than the sum of its proper divisors (1484711574).

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

666566100 is a wasteful number, since it uses less digits than its factorization.

666566100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635 (or 588 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 36.

The square root of 666566100 is about 25817.9414361409. The cubic root of 666566100 is about 873.5365359896.

It can be divided in two parts, 666566 and 100, that added together give a palindrome (666666).

The spelling of 666566100 in words is "six hundred sixty-six million, five hundred sixty-six thousand, one hundred".