491791389840 has 640 divisors, whose sum is σ = 1815598080000. Its totient is φ = 123522319872.

The previous prime is 491791389839. The next prime is 491791389853. The reversal of 491791389840 is 48983197194.

491791389840 is a `hidden beast` number, since 4 + 9 + 179 + 1 + 389 + 84 + 0 = 666.

It is a super-2 number, since 2×491791389840² (a number of 24 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 794493051 + ... + 794493669.

It is an arithmetic number, because the mean of its divisors is an integer number (2836872000).

Almost surely, 2^491791389840 is an apocalyptic number.

491791389840 is a gapful number since it is divisible by the number (40) 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 491791389840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (907799040000).

491791389840 is an abundant number, since it is smaller than the sum of its proper divisors (1323806690160).

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

491791389840 is a wasteful number, since it uses less digits than its factorization.

491791389840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 911 (or 887 counting only the distinct ones).

The product of its (nonzero) digits is 15676416, while the sum is 63.

The spelling of 491791389840 in words is "four hundred ninety-one billion, seven hundred ninety-one million, three hundred eighty-nine thousand, eight hundred forty".