685989 has 14 divisors (see below), whose sum is σ = 1029606. Its totient is φ = 456840.

The previous prime is 685987. The next prime is 685991. The reversal of 685989 is 989586.

It is an interprime number because it is at equal distance from previous prime (685987) and next prime (685991).

It can be written as a sum of positive squares in only one way, i.e., 613089 + 72900 = 783^2 + 270^2 .

It is not a de Polignac number, because 685989 - 2¹ = 685987 is a prime.

685989 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685987) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 259 + ... + 1199.

2⁶⁸⁵⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

685989 is a deficient number, since it is larger than the sum of its proper divisors (343617).

685989 is an frugal number, since it uses more digits than its factorization.

685989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 959 (or 944 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 685989 is about 828.2445291096. The cubic root of 685989 is about 88.1940020911.

The spelling of 685989 in words is "six hundred eighty-five thousand, nine hundred eighty-nine".