666681840 has 400 divisors, whose sum is σ = 2592691200. Its totient is φ = 157386240.

The previous prime is 666681839. The next prime is 666681857. The reversal of 666681840 is 48186666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 3350061 + ... + 3350259.

It is an arithmetic number, because the mean of its divisors is an integer number (6481728).

Almost surely, 2^666681840 is an apocalyptic number.

666681840 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 666681840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1296345600).

666681840 is an abundant number, since it is smaller than the sum of its proper divisors (1926009360).

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

666681840 is a wasteful number, since it uses less digits than its factorization.

666681840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 45.

The square root of 666681840 is about 25820.1828033808. The cubic root of 666681840 is about 873.5870922498.

The spelling of 666681840 in words is "six hundred sixty-six million, six hundred eighty-one thousand, eight hundred forty".