491778194987557 has 2 divisors, whose sum is σ = 491778194987558. Its totient is φ = 491778194987556.

The previous prime is 491778194987507. The next prime is 491778194987587. The reversal of 491778194987557 is 755789491877194.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 409275598374721 + 82502596612836 = 20230561^2 + 9083094^2 .

It is a cyclic number.

It is not a de Polignac number, because 491778194987557 - 2⁴⁷ = 351040706632229 is a prime.

It is a super-3 number, since 3×491778194987557³ (a number of 45 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (491778194987507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 245889097493778 + 245889097493779.

It is an arithmetic number, because the mean of its divisors is an integer number (245889097493779).

Almost surely, 2^{491778194987557} is an apocalyptic number.

It is an amenable number.

491778194987557 is a deficient number, since it is larger than the sum of its proper divisors (1).

491778194987557 is an equidigital number, since it uses as much as digits as its factorization.

491778194987557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 44808422400, while the sum is 91.

The spelling of 491778194987557 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 fifty-seven".