778381917961 has 4 divisors (see below), whose sum is σ = 778554397972. Its totient is φ = 778209437952.

The previous prime is 778381917953. The next prime is 778381918003. The reversal of 778381917961 is 169719183877.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 169719183877 = 6491 ⋅26146847.

It can be written as a sum of positive squares in 2 ways, for example, as 1445444361 + 776936473600 = 38019^2 + 881440^2 .

It is a cyclic number.

It is not a de Polignac number, because 778381917961 - 2³ = 778381917953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (778381017961) 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 in 3 ways as a sum of consecutive naturals, for example, 86233236 + ... + 86242261.

It is an arithmetic number, because the mean of its divisors is an integer number (194638599493).

Almost surely, 2^778381917961 is an apocalyptic number.

It is an amenable number.

778381917961 is a deficient number, since it is larger than the sum of its proper divisors (172480011).

778381917961 is a wasteful number, since it uses less digits than its factorization.

778381917961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172480010.

The product of its digits is 32006016, while the sum is 67.

The spelling of 778381917961 in words is "seven hundred seventy-eight billion, three hundred eighty-one million, nine hundred seventeen thousand, nine hundred sixty-one".