78209 has 4 divisors (see below), whose sum is σ = 78804. Its totient is φ = 77616.

The previous prime is 78203. The next prime is 78229. The reversal of 78209 is 90287.

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 67600 + 10609 = 260^2 + 103^2 .

It is a cyclic number.

It is not a de Polignac number, because 78209 - 2⁴ = 78193 is a prime.

It is a super-2 number, since 2×78209² = 12233295362, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 78209.

It is not an unprimeable number, because it can be changed into a prime (78203) 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, 2 + ... + 395.

It is an arithmetic number, because the mean of its divisors is an integer number (19701).

2⁷⁸²⁰⁹ is an apocalyptic number.

It is an amenable number.

78209 is a deficient number, since it is larger than the sum of its proper divisors (595).

78209 is a wasteful number, since it uses less digits than its factorization.

78209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 78209 is about 279.6587205864. The cubic root of 78209 is about 42.7647145635.

The spelling of 78209 in words is "seventy-eight thousand, two hundred nine".