640731812 has 48 divisors (see below), whose sum is σ = 1320926208. Its totient is φ = 266198400.

The previous prime is 640731811. The next prime is 640731827. The reversal of 640731812 is 218137046.

It is not an unprimeable number, because it can be changed into a prime (640731811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 327437 + ... + 329387.

It is an arithmetic number, because the mean of its divisors is an integer number (27519296).

Almost surely, 2^640731812 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640731812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (660463104).

640731812 is an abundant number, since it is smaller than the sum of its proper divisors (680194396).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640731812 is a wasteful number, since it uses less digits than its factorization.

640731812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2316 (or 2314 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 640731812 is about 25312.6808536749. The cubic root of 640731812 is about 862.1022178046.

Adding to 640731812 its reverse (218137046), we get a palindrome (858868858).

The spelling of 640731812 in words is "six hundred forty million, seven hundred thirty-one thousand, eight hundred twelve".