640340 has 24 divisors (see below), whose sum is σ = 1362312. Its totient is φ = 252800.

The previous prime is 640333. The next prime is 640363. The reversal of 640340 is 43046.

640340 = T₄₅₉ + T₄₆₀ + ... + T₄₆₄.

It can be written as a sum of positive squares in 4 ways, for example, as 71824 + 568516 = 268^2 + 754^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1862 + ... + 2178.

It is an arithmetic number, because the mean of its divisors is an integer number (56763).

2⁶⁴⁰³⁴⁰ is an apocalyptic number.

It is an amenable number.

640340 is an abundant number, since it is smaller than the sum of its proper divisors (721972).

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

640340 is a wasteful number, since it uses less digits than its factorization.

640340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427 (or 425 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 17.

The square root of 640340 is about 800.2124717848. The cubic root of 640340 is about 86.1926454787.

Adding to 640340 its reverse (43046), we get a palindrome (683386).

The spelling of 640340 in words is "six hundred forty thousand, three hundred forty".