640018 has 4 divisors (see below), whose sum is σ = 960030. Its totient is φ = 320008.

The previous prime is 640009. The next prime is 640019. The reversal of 640018 is 810046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 351649 + 288369 = 593^2 + 537^2 .

It is a junction number, because it is equal to n+sod(n) for n = 639977 and 640004.

It is not an unprimeable number, because it can be changed into a prime (640019) 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 as a sum of consecutive naturals, namely, 160003 + ... + 160006.

2⁶⁴⁰⁰¹⁸ is an apocalyptic number.

640018 is a deficient number, since it is larger than the sum of its proper divisors (320012).

640018 is a wasteful number, since it uses less digits than its factorization.

640018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320011.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 640018 is about 800.0112499209. The cubic root of 640018 is about 86.1781955067.

It can be divided in two parts, 64001 and 8, that added together give a square (64009 = 253²).

The spelling of 640018 in words is "six hundred forty thousand, eighteen".