640306 has 4 divisors (see below), whose sum is σ = 960462. Its totient is φ = 320152.

The previous prime is 640303. The next prime is 640307. The reversal of 640306 is 603046.

It is a happy number.

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., 632025 + 8281 = 795^2 + 91^2 .

It is not an unprimeable number, because it can be changed into a prime (640303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160075 + ... + 160078.

2⁶⁴⁰³⁰⁶ is an apocalyptic number.

640306 is a deficient number, since it is larger than the sum of its proper divisors (320156).

640306 is a wasteful number, since it uses less digits than its factorization.

640306 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320155.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 640306 is about 800.1912271451. The cubic root of 640306 is about 86.1911199341.

It can be divided in two parts, 640 and 306, that added together give a triangular number (946 = T₄₃).

The spelling of 640306 in words is "six hundred forty thousand, three hundred six".