685778 has 4 divisors (see below), whose sum is σ = 1028670. Its totient is φ = 342888.

The previous prime is 685759. The next prime is 685781. The reversal of 685778 is 877586.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877586 = 2 ⋅438793.

It can be written as a sum of positive squares in only one way, i.e., 683929 + 1849 = 827^2 + 43^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 171443 + ... + 171446.

2⁶⁸⁵⁷⁷⁸ is an apocalyptic number.

685778 is a deficient number, since it is larger than the sum of its proper divisors (342892).

685778 is a wasteful number, since it uses less digits than its factorization.

685778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 342891.

The product of its digits is 94080, while the sum is 41.

The square root of 685778 is about 828.1171414721. The cubic root of 685778 is about 88.1849587766.

The spelling of 685778 in words is "six hundred eighty-five thousand, seven hundred seventy-eight".