640505 has 8 divisors (see below), whose sum is σ = 783432. Its totient is φ = 502528.

The previous prime is 640499. The next prime is 640529. The reversal of 640505 is 505046.

It can be written as a sum of positive squares in 4 ways, for example, as 295936 + 344569 = 544^2 + 587^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640505 - 2⁸ = 640249 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640505.

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, 944 + ... + 1473.

It is an arithmetic number, because the mean of its divisors is an integer number (97929).

2⁶⁴⁰⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

640505 is a deficient number, since it is larger than the sum of its proper divisors (142927).

640505 is a wasteful number, since it uses less digits than its factorization.

640505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2475.

The product of its (nonzero) digits is 600, while the sum is 20.

The square root of 640505 is about 800.3155627626. The cubic root of 640505 is about 86.2000480904.

The spelling of 640505 in words is "six hundred forty thousand, five hundred five".