640423 has 8 divisors (see below), whose sum is σ = 737280. Its totient is φ = 544920.

The previous prime is 640421. The next prime is 640457. The reversal of 640423 is 324046.

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 640423 - 2¹ = 640421 is a prime.

It is an Ulam number.

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 640423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1098 + ... + 1576.

It is an arithmetic number, because the mean of its divisors is an integer number (92160).

2⁶⁴⁰⁴²³ is an apocalyptic number.

640423 is a deficient number, since it is larger than the sum of its proper divisors (96857).

640423 is a wasteful number, since it uses less digits than its factorization.

640423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 677.

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 640423 is about 800.2643313306. The cubic root of 640423 is about 86.1963693757.

Adding to 640423 its reverse (324046), we get a palindrome (964469).

The spelling of 640423 in words is "six hundred forty thousand, four hundred twenty-three".