666221760 has 140 divisors (see below), whose sum is σ = 2369960208. Its totient is φ = 177652224.

The previous prime is 666221753. The next prime is 666221779. The reversal of 666221760 is 67122666.

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

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 13069 + ... + 38771.

Almost surely, 2^666221760 is an apocalyptic number.

666221760 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 666221760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1184980104).

666221760 is an abundant number, since it is smaller than the sum of its proper divisors (1703738448).

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

666221760 is a wasteful number, since it uses less digits than its factorization.

666221760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25732 (or 25713 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 36.

The square root of 666221760 is about 25811.2719562597. The cubic root of 666221760 is about 873.3860906044.

The spelling of 666221760 in words is "six hundred sixty-six million, two hundred twenty-one thousand, seven hundred sixty".