640040 has 16 divisors (see below), whose sum is σ = 1440180. Its totient is φ = 256000.

The previous prime is 640039. The next prime is 640043. The reversal of 640040 is 40046.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 630436 + 9604 = 794^2 + 98^2 .

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 639997 and 640024.

It is not an unprimeable number, because it can be changed into a prime (640043) by changing a digit.

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, 7961 + ... + 8040.

2⁶⁴⁰⁰⁴⁰ is an apocalyptic number.

It is an amenable number.

640040 is an abundant number, since it is smaller than the sum of its proper divisors (800140).

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

640040 is a wasteful number, since it uses less digits than its factorization.

640040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16012 (or 16008 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 640040 is about 800.0249996094. The cubic root of 640040 is about 86.1791829261.

Adding to 640040 its reverse (40046), we get a palindrome (680086).

The spelling of 640040 in words is "six hundred forty thousand, forty".