778981891 has 2 divisors, whose sum is σ = 778981892. Its totient is φ = 778981890.

The previous prime is 778981883. The next prime is 778981913. The reversal of 778981891 is 198189877.

It is a weak prime.

It is an emirp because it is prime and its reverse (198189877) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 778981891 - 2³ = 778981883 is a prime.

It is not a weakly prime, because it can be changed into another prime (778981391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 389490945 + 389490946.

It is an arithmetic number, because the mean of its divisors is an integer number (389490946).

Almost surely, 2^778981891 is an apocalyptic number.

778981891 is a deficient number, since it is larger than the sum of its proper divisors (1).

778981891 is an equidigital number, since it uses as much as digits as its factorization.

778981891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2032128, while the sum is 58.

The square root of 778981891 is about 27910.2470608915. The cubic root of 778981891 is about 920.1157270142.

The spelling of 778981891 in words is "seven hundred seventy-eight million, nine hundred eighty-one thousand, eight hundred ninety-one".