7776687661 has 4 divisors (see below), whose sum is σ = 7776886300. Its totient is φ = 7776489024.

The previous prime is 7776687649. The next prime is 7776687671. The reversal of 7776687661 is 1667866777.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1667866777 = 6197 ⋅269141.

It can be written as a sum of positive squares in 2 ways, for example, as 4095232036 + 3681455625 = 63994^2 + 60675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7776687661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7776687661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7776687601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18876 + ... + 126133.

It is an arithmetic number, because the mean of its divisors is an integer number (1944221575).

Almost surely, 2^7776687661 is an apocalyptic number.

It is an amenable number.

7776687661 is a deficient number, since it is larger than the sum of its proper divisors (198639).

7776687661 is a wasteful number, since it uses less digits than its factorization.

7776687661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198638.

The product of its digits is 24893568, while the sum is 61.

The square root of 7776687661 is about 88185.5297710458. The cubic root of 7776687661 is about 1981.2147479907.

The spelling of 7776687661 in words is "seven billion, seven hundred seventy-six million, six hundred eighty-seven thousand, six hundred sixty-one".