78817 has 4 divisors (see below), whose sum is σ = 79380. Its totient is φ = 78256.

The previous prime is 78809. The next prime is 78823. The reversal of 78817 is 71887.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 40401 + 38416 = 201^2 + 196^2 .

It is a cyclic number.

It is not a de Polignac number, because 78817 - 2³ = 78809 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78857) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123 + ... + 415.

It is an arithmetic number, because the mean of its divisors is an integer number (19845).

2⁷⁸⁸¹⁷ is an apocalyptic number.

It is an amenable number.

78817 is a deficient number, since it is larger than the sum of its proper divisors (563).

78817 is a wasteful number, since it uses less digits than its factorization.

78817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 562.

The product of its digits is 3136, while the sum is 31.

The square root of 78817 is about 280.7436553157. The cubic root of 78817 is about 42.8752468487.

The spelling of 78817 in words is "seventy-eight thousand, eight hundred seventeen".