640641 has 8 divisors (see below), whose sum is σ = 859680. Its totient is φ = 424352.

The previous prime is 640631. The next prime is 640649. The reversal of 640641 is 146046.

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 640641 - 2¹⁷ = 509569 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60 + ... + 1133.

It is an arithmetic number, because the mean of its divisors is an integer number (107460).

2⁶⁴⁰⁶⁴¹ is an apocalyptic number.

It is an amenable number.

640641 is a deficient number, since it is larger than the sum of its proper divisors (219039).

640641 is a wasteful number, since it uses less digits than its factorization.

640641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1375.

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 640641 is about 800.4005247375. The cubic root of 640641 is about 86.2061486813.

Adding to 640641 its reverse (146046), we get a palindrome (786687).

The spelling of 640641 in words is "six hundred forty thousand, six hundred forty-one".