491778194987521 has 32 divisors (see below), whose sum is σ = 570194277962400. Its totient is φ = 420111738224640.

The previous prime is 491778194987507. The next prime is 491778194987557. The reversal of 491778194987521 is 125789491877194.

It can be written as a sum of positive squares in 16 ways, for example, as 340846773265296 + 150931421722225 = 18462036^2 + 12285415^2 .

It is a cyclic number.

It is not a de Polignac number, because 491778194987521 - 2⁷ = 491778194987393 is a prime.

It is a Smith number, since the sum of its digits (82) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (491778194982521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 65508156 + ... + 72628333.

It is an arithmetic number, because the mean of its divisors is an integer number (17818571186325).

Almost surely, 2^{491778194987521} is an apocalyptic number.

It is an amenable number.

491778194987521 is a deficient number, since it is larger than the sum of its proper divisors (78416082974879).

491778194987521 is a wasteful number, since it uses less digits than its factorization.

491778194987521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138136789.

The product of its digits is 2560481280, while the sum is 82.

The spelling of 491778194987521 in words is "four hundred ninety-one trillion, seven hundred seventy-eight billion, one hundred ninety-four million, nine hundred eighty-seven thousand, five hundred twenty-one".