491581818 has 192 divisors, whose sum is σ = 1415715840. Its totient is φ = 125193600.

The previous prime is 491581771. The next prime is 491581819. The reversal of 491581818 is 818185194.

491581818 is a `hidden beast` number, since 491 + 5 + 81 + 81 + 8 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491581819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1066108 + ... + 1066568.

It is an arithmetic number, because the mean of its divisors is an integer number (7373520).

Almost surely, 2^491581818 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 491581818, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (707857920).

491581818 is an abundant number, since it is smaller than the sum of its proper divisors (924134022).

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

491581818 is a wasteful number, since it uses less digits than its factorization.

491581818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530 (or 517 counting only the distinct ones).

The product of its digits is 92160, while the sum is 45.

The square root of 491581818 is about 22171.6444586323. The cubic root of 491581818 is about 789.2209475329.

The spelling of 491581818 in words is "four hundred ninety-one million, five hundred eighty-one thousand, eight hundred eighteen".