78890809 has 2 divisors, whose sum is σ = 78890810. Its totient is φ = 78890808.

The previous prime is 78890741. The next prime is 78890813. The reversal of 78890809 is 90809887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 67815225 + 11075584 = 8235^2 + 3328^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78890809 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78890309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39445404 + 39445405.

It is an arithmetic number, because the mean of its divisors is an integer number (39445405).

Almost surely, 2^78890809 is an apocalyptic number.

It is an amenable number.

78890809 is a deficient number, since it is larger than the sum of its proper divisors (1).

78890809 is an equidigital number, since it uses as much as digits as its factorization.

78890809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 290304, while the sum is 49.

The square root of 78890809 is about 8882.0498197207. The cubic root of 78890809 is about 428.8862633015.

The spelling of 78890809 in words is "seventy-eight million, eight hundred ninety thousand, eight hundred nine".