640168 has 8 divisors (see below), whose sum is σ = 1200330. Its totient is φ = 320080.

The previous prime is 640163. The next prime is 640193. The reversal of 640168 is 861046.

It can be written as a sum of positive squares in only one way, i.e., 636804 + 3364 = 798^2 + 58^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (640163) by changing a digit.

640168 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40003 + ... + 40018.

2⁶⁴⁰¹⁶⁸ is an apocalyptic number.

It is an amenable number.

640168 is a deficient number, since it is larger than the sum of its proper divisors (560162).

640168 is a wasteful number, since it uses less digits than its factorization.

640168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80027 (or 80023 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 640168 is about 800.1049931103. The cubic root of 640168 is about 86.1849274630.

It can be divided in two parts, 640 and 168, that added together give a palindrome (808).

The spelling of 640168 in words is "six hundred forty thousand, one hundred sixty-eight".