666581916 has 192 divisors, whose sum is σ = 2106187776. Its totient is φ = 158457600.

The previous prime is 666581897. The next prime is 666581939. The reversal of 666581916 is 619185666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2534401 + ... + 2534663.

It is an arithmetic number, because the mean of its divisors is an integer number (10969728).

Almost surely, 2^666581916 is an apocalyptic number.

666581916 is a gapful number since it is divisible by the number (66) 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 666581916, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1053093888).

666581916 is an abundant number, since it is smaller than the sum of its proper divisors (1439605860).

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

666581916 is a wasteful number, since it uses less digits than its factorization.

666581916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 512 (or 510 counting only the distinct ones).

The product of its digits is 466560, while the sum is 48.

The square root of 666581916 is about 25818.2477329504. The cubic root of 666581916 is about 873.5434449041.

The spelling of 666581916 in words is "six hundred sixty-six million, five hundred eighty-one thousand, nine hundred sixteen".