646685 has 8 divisors (see below), whose sum is σ = 835800. Its totient is φ = 477504.

The previous prime is 646669. The next prime is 646687. The reversal of 646685 is 586646.

It can be written as a sum of positive squares in 4 ways, for example, as 3481 + 643204 = 59^2 + 802^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 646685 - 2⁴ = 646669 is a prime.

It is a super-3 number, since 3×646685³ = 811333890178407375, which contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646687) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4910 + ... + 5039.

It is an arithmetic number, because the mean of its divisors is an integer number (104475).

2⁶⁴⁶⁶⁸⁵ is an apocalyptic number.

646685 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

646685 is a deficient number, since it is larger than the sum of its proper divisors (189115).

646685 is a wasteful number, since it uses less digits than its factorization.

646685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9967.

The product of its digits is 34560, while the sum is 35.

The square root of 646685 is about 804.1672711569. The cubic root of 646685 is about 86.4763988314.

It can be divided in two parts, 646 and 685, that added together give a palindrome (1331).

The spelling of 646685 in words is "six hundred forty-six thousand, six hundred eighty-five".