78784891 has 2 divisors, whose sum is σ = 78784892. Its totient is φ = 78784890.

The previous prime is 78784889. The next prime is 78784897. The reversal of 78784891 is 19848787.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78784891 - 2¹ = 78784889 is a prime.

Together with 78784889, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (78784897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39392445 + 39392446.

It is an arithmetic number, because the mean of its divisors is an integer number (39392446).

Almost surely, 2^78784891 is an apocalyptic number.

78784891 is a deficient number, since it is larger than the sum of its proper divisors (1).

78784891 is an equidigital number, since it uses as much as digits as its factorization.

78784891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 903168, while the sum is 52.

The square root of 78784891 is about 8876.0853420863. The cubic root of 78784891 is about 428.6942378897.

It can be divided in two parts, 7878 and 4891, that added together give a square (12769 = 113²).

The spelling of 78784891 in words is "seventy-eight million, seven hundred eighty-four thousand, eight hundred ninety-one".