640031 has 4 divisors (see below), whose sum is σ = 731472. Its totient is φ = 548592.

The previous prime is 640027. The next prime is 640039. The reversal of 640031 is 130046.

640031 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.

It is a cyclic number.

It is not a de Polignac number, because 640031 - 2² = 640027 is a prime.

It is a super-2 number, since 2×640031² = 819279361922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 639988 and 640015.

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 640031.

It is not an unprimeable number, because it can be changed into a prime (640039) 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, 45710 + ... + 45723.

It is an arithmetic number, because the mean of its divisors is an integer number (182868).

2⁶⁴⁰⁰³¹ is an apocalyptic number.

640031 is a deficient number, since it is larger than the sum of its proper divisors (91441).

640031 is an equidigital number, since it uses as much as digits as its factorization.

640031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91440.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 640031 is about 800.0193747654. The cubic root of 640031 is about 86.1787789845.

Adding to 640031 its reverse (130046), we get a palindrome (770077).

The spelling of 640031 in words is "six hundred forty thousand, thirty-one".