640047 has 4 divisors (see below), whose sum is σ = 853400. Its totient is φ = 426696.

The previous prime is 640043. The next prime is 640049. The reversal of 640047 is 740046.

640047 is nontrivially palindromic in base 15.

640047 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 not a de Polignac number, because 640047 - 2² = 640043 is a prime.

It is a D-number.

It is a Duffinian number.

640047 is a lucky 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 640047.

It is not an unprimeable number, because it can be changed into a prime (640043) 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, 106672 + ... + 106677.

It is an arithmetic number, because the mean of its divisors is an integer number (213350).

2⁶⁴⁰⁰⁴⁷ is an apocalyptic number.

640047 is a deficient number, since it is larger than the sum of its proper divisors (213353).

640047 is a wasteful number, since it uses less digits than its factorization.

640047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213352.

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 640047 is about 800.0293744607. The cubic root of 640047 is about 86.1794971003.

Subtracting 640047 from its reverse (740046), we obtain a palindrome (99999).

The spelling of 640047 in words is "six hundred forty thousand, forty-seven".