7777777777681 has 2 divisors, whose sum is σ = 7777777777682. Its totient is φ = 7777777777680.

The previous prime is 7777777777661. The next prime is 7777777777691. The reversal of 7777777777681 is 1867777777777.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6818913803025 + 958863974656 = 2611305^2 + 979216^2 .

It is an emirp because it is prime and its reverse (1867777777777) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7777777777681 - 2¹¹ = 7777777775633 is a prime.

It is a super-2 number, since 2×7777777777681² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (7777777777631) 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 as a sum of consecutive naturals, namely, 3888888888840 + 3888888888841.

It is an arithmetic number, because the mean of its divisors is an integer number (3888888888841).

Almost surely, 2^{7777777777681} is an apocalyptic number.

It is an amenable number.

7777777777681 is a deficient number, since it is larger than the sum of its proper divisors (1).

7777777777681 is an equidigital number, since it uses as much as digits as its factorization.

7777777777681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13558811952, while the sum is 85.

The spelling of 7777777777681 in words is "seven trillion, seven hundred seventy-seven billion, seven hundred seventy-seven million, seven hundred seventy-seven thousand, six hundred eighty-one".