640289 has 4 divisors (see below), whose sum is σ = 689556. Its totient is φ = 591024.

The previous prime is 640279. The next prime is 640303. The reversal of 640289 is 982046.

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

It can be written as a sum of positive squares in 2 ways, for example, as 85264 + 555025 = 292^2 + 745^2 .

It is a cyclic number.

It is not a de Polignac number, because 640289 - 2¹² = 636193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640219) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24614 + ... + 24639.

It is an arithmetic number, because the mean of its divisors is an integer number (172389).

2⁶⁴⁰²⁸⁹ is an apocalyptic number.

It is an amenable number.

640289 is a deficient number, since it is larger than the sum of its proper divisors (49267).

640289 is a wasteful number, since it uses less digits than its factorization.

640289 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49266.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 640289 is about 800.1806046137. The cubic root of 640289 is about 86.1903571415.

It can be divided in two parts, 6402 and 89, that multiplied together give a triangular number (569778 = T₁₀₆₇).

The spelling of 640289 in words is "six hundred forty thousand, two hundred eighty-nine".