640431 has 12 divisors (see below), whose sum is σ = 1009320. Its totient is φ = 388080.

The previous prime is 640421. The next prime is 640457. The reversal of 640431 is 134046.

640431 = 160² + 161² + ... + 181².

It is not a de Polignac number, because 640431 - 2⁷ = 640303 is a prime.

It is a super-2 number, since 2×640431² = 820303731522, which contains 22 as substring.

It is a congruent number.

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 11 ways as a sum of consecutive naturals, for example, 3136 + ... + 3333.

It is an arithmetic number, because the mean of its divisors is an integer number (84110).

2⁶⁴⁰⁴³¹ is an apocalyptic number.

640431 is a deficient number, since it is larger than the sum of its proper divisors (368889).

640431 is a wasteful number, since it uses less digits than its factorization.

640431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6486 (or 6483 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 640431 is about 800.2693296635. The cubic root of 640431 is about 86.1967282885.

Adding to 640431 its reverse (134046), we get a palindrome (774477).

The spelling of 640431 in words is "six hundred forty thousand, four hundred thirty-one".