640217 has 4 divisors (see below), whose sum is σ = 642000. Its totient is φ = 638436.

The previous prime is 640193. The next prime is 640219. The reversal of 640217 is 712046.

640217 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 712046 = 2 ⋅356023.

It is a cyclic number.

It is not a de Polignac number, because 640217 - 2⁶ = 640153 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, 143 + ... + 1140.

It is an arithmetic number, because the mean of its divisors is an integer number (160500).

2⁶⁴⁰²¹⁷ is an apocalyptic number.

It is an amenable number.

640217 is a deficient number, since it is larger than the sum of its proper divisors (1783).

640217 is a wasteful number, since it uses less digits than its factorization.

640217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1782.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 640217 is about 800.1356135056. The cubic root of 640217 is about 86.1871263408.

The spelling of 640217 in words is "six hundred forty thousand, two hundred seventeen".