640511 has 4 divisors (see below), whose sum is σ = 648312. Its totient is φ = 632712.

The previous prime is 640499. The next prime is 640529. The reversal of 640511 is 115046.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 640511 - 2¹⁰ = 639487 is a prime.

It is a super-2 number, since 2×640511² = 820508682242, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 640511.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640531) 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, 3776 + ... + 3941.

It is an arithmetic number, because the mean of its divisors is an integer number (162078).

2⁶⁴⁰⁵¹¹ is an apocalyptic number.

640511 is a deficient number, since it is larger than the sum of its proper divisors (7801).

640511 is an equidigital number, since it uses as much as digits as its factorization.

640511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7800.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 640511 is about 800.3193112752. The cubic root of 640511 is about 86.2003172524.

Adding to 640511 its reverse (115046), we get a palindrome (755557).

The spelling of 640511 in words is "six hundred forty thousand, five hundred eleven".