666641220 has 192 divisors, whose sum is σ = 2265446400. Its totient is φ = 143078400.

The previous prime is 666641203. The next prime is 666641221. The reversal of 666641220 is 22146666.

It is not an unprimeable number, because it can be changed into a prime (666641221) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1108920 + ... + 1109520.

It is an arithmetic number, because the mean of its divisors is an integer number (11799200).

Almost surely, 2^666641220 is an apocalyptic number.

666641220 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 666641220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1132723200).

666641220 is an abundant number, since it is smaller than the sum of its proper divisors (1598805180).

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

666641220 is a wasteful number, since it uses less digits than its factorization.

666641220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778 (or 776 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 33.

The square root of 666641220 is about 25819.3961974327. The cubic root of 666641220 is about 873.5693497394.

Adding to 666641220 its reverse (22146666), we get a palindrome (688787886).

The spelling of 666641220 in words is "six hundred sixty-six million, six hundred forty-one thousand, two hundred twenty".