778888861 has 2 divisors, whose sum is σ = 778888862. Its totient is φ = 778888860.

The previous prime is 778888853. The next prime is 778888909. The reversal of 778888861 is 168888877.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 630512100 + 148376761 = 25110^2 + 12181^2 .

It is a cyclic number.

It is not a de Polignac number, because 778888861 - 2³ = 778888853 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 778888861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (778808861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 389444430 + 389444431.

It is an arithmetic number, because the mean of its divisors is an integer number (389444431).

Almost surely, 2^778888861 is an apocalyptic number.

It is an amenable number.

778888861 is a deficient number, since it is larger than the sum of its proper divisors (1).

778888861 is an equidigital number, since it uses as much as digits as its factorization.

778888861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9633792, while the sum is 61.

The square root of 778888861 is about 27908.5804189321. The cubic root of 778888861 is about 920.0790972479.

The spelling of 778888861 in words is "seven hundred seventy-eight million, eight hundred eighty-eight thousand, eight hundred sixty-one".