640431331 has 8 divisors (see below), whose sum is σ = 665294400. Its totient is φ = 615753600.

The previous prime is 640431329. The next prime is 640431377. The reversal of 640431331 is 133134046.

It is a happy number.

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 640431331 - 2¹ = 640431329 is a prime.

It is a super-2 number, since 2×640431331² = 820304579452863122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640431296 and 640431305.

It is not an unprimeable number, because it can be changed into a prime (640434331) 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, 39270 + ... + 53131.

It is an arithmetic number, because the mean of its divisors is an integer number (83161800).

Almost surely, 2^640431331 is an apocalyptic number.

640431331 is a deficient number, since it is larger than the sum of its proper divisors (24863069).

640431331 is a wasteful number, since it uses less digits than its factorization.

640431331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92669.

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 640431331 is about 25306.7447728861. The cubic root of 640431331 is about 861.9674313845.

Adding to 640431331 its reverse (133134046), we get a palindrome (773565377).

The spelling of 640431331 in words is "six hundred forty million, four hundred thirty-one thousand, three hundred thirty-one".