640236840 has 32 divisors (see below), whose sum is σ = 1920710880. Its totient is φ = 170729792.

The previous prime is 640236833. The next prime is 640236841. The reversal of 640236840 is 48632046.

640236840 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×640236840² = 819806422586371200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640236841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2667534 + ... + 2667773.

It is an arithmetic number, because the mean of its divisors is an integer number (60022215).

Almost surely, 2^640236840 is an apocalyptic number.

640236840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640236840 is an abundant number, since it is smaller than the sum of its proper divisors (1280474040).

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

640236840 is a wasteful number, since it uses less digits than its factorization.

640236840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5335321 (or 5335317 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 33.

The square root of 640236840 is about 25302.9018098715. The cubic root of 640236840 is about 861.8801663008.

Adding to 640236840 its reverse (48632046), we get a palindrome (688868886).

The spelling of 640236840 in words is "six hundred forty million, two hundred thirty-six thousand, eight hundred forty".