685978 has 4 divisors (see below), whose sum is σ = 1028970. Its totient is φ = 342988.

The previous prime is 685973. The next prime is 685987. The reversal of 685978 is 879586.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 677329 + 8649 = 823^2 + 93^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (685973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 171493 + ... + 171496.

2⁶⁸⁵⁹⁷⁸ is an apocalyptic number.

685978 is a deficient number, since it is larger than the sum of its proper divisors (342992).

685978 is a wasteful number, since it uses less digits than its factorization.

685978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342991.

The product of its digits is 120960, while the sum is 43.

The square root of 685978 is about 828.2378885320. The cubic root of 685978 is about 88.1935306845.

The spelling of 685978 in words is "six hundred eighty-five thousand, nine hundred seventy-eight".