640401 has 4 divisors (see below), whose sum is σ = 853872. Its totient is φ = 426932.

The previous prime is 640369. The next prime is 640411. The reversal of 640401 is 104046.

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.

It is a cyclic number.

It is not a de Polignac number, because 640401 - 2⁵ = 640369 is a prime.

It is a super-2 number, since 2×640401² = 820226881602, which contains 22 as substring.

It is an Ulam number.

It is a D-number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640401.

It is not an unprimeable number, because it can be changed into a prime (640411) 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, 106731 + ... + 106736.

It is an arithmetic number, because the mean of its divisors is an integer number (213468).

2⁶⁴⁰⁴⁰¹ is an apocalyptic number.

It is an amenable number.

640401 is a deficient number, since it is larger than the sum of its proper divisors (213471).

640401 is a wasteful number, since it uses less digits than its factorization.

640401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213470.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 640401 is about 800.2505857542. The cubic root of 640401 is about 86.1953823500.

Adding to 640401 its reverse (104046), we get a palindrome (744447).

The spelling of 640401 in words is "six hundred forty thousand, four hundred one".