640449 has 6 divisors (see below), whose sum is σ = 925106. Its totient is φ = 426960.

The previous prime is 640421. The next prime is 640457. The reversal of 640449 is 944046.

It can be written as a sum of positive squares in only one way, i.e., 589824 + 50625 = 768^2 + 225^2 .

It is not a de Polignac number, because 640449 - 2⁸ = 640193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640499) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35572 + ... + 35589.

2⁶⁴⁰⁴⁴⁹ is an apocalyptic number.

It is an amenable number.

640449 is a deficient number, since it is larger than the sum of its proper divisors (284657).

640449 is a wasteful number, since it uses less digits than its factorization.

640449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71167 (or 71164 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 640449 is about 800.2805757983. The cubic root of 640449 is about 86.1975358314.

It can be divided in two parts, 640 and 449, that added together give a square (1089 = 33²).

The spelling of 640449 in words is "six hundred forty thousand, four hundred forty-nine".