668240 has 20 divisors (see below), whose sum is σ = 1553844. Its totient is φ = 267264.

The previous prime is 668221. The next prime is 668243. The reversal of 668240 is 42866.

It can be written as a sum of positive squares in 2 ways, for example, as 341056 + 327184 = 584^2 + 572^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668243) by changing a digit.

668240 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4097 + ... + 4256.

2⁶⁶⁸²⁴⁰ is an apocalyptic number.

It is an amenable number.

668240 is an abundant number, since it is smaller than the sum of its proper divisors (885604).

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

668240 is a wasteful number, since it uses less digits than its factorization.

668240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8366 (or 8360 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 668240 is about 817.4594791181. The cubic root of 668240 is about 87.4267141466.

The spelling of 668240 in words is "six hundred sixty-eight thousand, two hundred forty".