78009 has 4 divisors (see below), whose sum is σ = 104016. Its totient is φ = 52004.

The previous prime is 78007. The next prime is 78017. The reversal of 78009 is 90087.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90087 = 3 ⋅30029.

It is a cyclic number.

It is not a de Polignac number, because 78009 - 2¹ = 78007 is a prime.

It is a D-number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 78009.

It is not an unprimeable number, because it can be changed into a prime (78007) 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, 12999 + ... + 13004.

It is an arithmetic number, because the mean of its divisors is an integer number (26004).

2⁷⁸⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

78009 is a deficient number, since it is larger than the sum of its proper divisors (26007).

78009 is a wasteful number, since it uses less digits than its factorization.

78009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26006.

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 78009 is about 279.3009129953. The cubic root of 78009 is about 42.7282300840.

The spelling of 78009 in words is "seventy-eight thousand, nine".