77905555661 has 2 divisors, whose sum is σ = 77905555662. Its totient is φ = 77905555660.

The previous prime is 77905555627. The next prime is 77905555681. The reversal of 77905555661 is 16655550977.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61910894761 + 15994660900 = 248819^2 + 126470^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77905555661 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 77905555597 and 77905555606.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77905555621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38952777830 + 38952777831.

It is an arithmetic number, because the mean of its divisors is an integer number (38952777831).

Almost surely, 2^77905555661 is an apocalyptic number.

It is an amenable number.

77905555661 is a deficient number, since it is larger than the sum of its proper divisors (1).

77905555661 is an equidigital number, since it uses as much as digits as its factorization.

77905555661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9922500, while the sum is 56.

The spelling of 77905555661 in words is "seventy-seven billion, nine hundred five million, five hundred fifty-five thousand, six hundred sixty-one".