78809 has 2 divisors, whose sum is σ = 78810. Its totient is φ = 78808.

The previous prime is 78803. The next prime is 78823. The reversal of 78809 is 90887.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40000 + 38809 = 200^2 + 197^2 .

It is an emirp because it is prime and its reverse (90887) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78809 - 2⁸ = 78553 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39404 + 39405.

It is an arithmetic number, because the mean of its divisors is an integer number (39405).

2⁷⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

78809 is a deficient number, since it is larger than the sum of its proper divisors (1).

78809 is an equidigital number, since it uses as much as digits as its factorization.

78809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 78809 is about 280.7294070809. The cubic root of 78809 is about 42.8737961736.

The spelling of 78809 in words is "seventy-eight thousand, eight hundred nine".