646840 has 32 divisors (see below), whose sum is σ = 1478880. Its totient is φ = 254592.

The previous prime is 646837. The next prime is 646843. The reversal of 646840 is 48646.

It is an interprime number because it is at equal distance from previous prime (646837) and next prime (646843).

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 646799 and 646808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646843) 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, 4042 + ... + 4198.

It is an arithmetic number, because the mean of its divisors is an integer number (46215).

2⁶⁴⁶⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

646840 is an abundant number, since it is smaller than the sum of its proper divisors (832040).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

646840 is a wasteful number, since it uses less digits than its factorization.

646840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 646840 is about 804.2636383674. The cubic root of 646840 is about 86.4833072804.

The spelling of 646840 in words is "six hundred forty-six thousand, eight hundred forty".