78665 has 4 divisors (see below), whose sum is σ = 94404. Its totient is φ = 62928.

The previous prime is 78653. The next prime is 78691. The reversal of 78665 is 56687.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17161 + 61504 = 131^2 + 248^2 .

It is a cyclic number.

It is not a de Polignac number, because 78665 - 2⁴ = 78649 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7862 + ... + 7871.

It is an arithmetic number, because the mean of its divisors is an integer number (23601).

2⁷⁸⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

78665 is a deficient number, since it is larger than the sum of its proper divisors (15739).

78665 is a wasteful number, since it uses less digits than its factorization.

78665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15738.

The product of its digits is 10080, while the sum is 32.

The square root of 78665 is about 280.4728150820. The cubic root of 78665 is about 42.8476672173.

The spelling of 78665 in words is "seventy-eight thousand, six hundred sixty-five".