640081944 has 48 divisors (see below), whose sum is σ = 1780415520. Its totient is φ = 207593280.

The previous prime is 640081931. The next prime is 640081963. The reversal of 640081944 is 449180046.

It is a happy number.

640081944 is a `hidden beast` number, since 640 + 0 + 8 + 1 + 9 + 4 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 640081899 and 640081908.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 117472 + ... + 122799.

It is an arithmetic number, because the mean of its divisors is an integer number (37091990).

Almost surely, 2^640081944 is an apocalyptic number.

It is an amenable number.

640081944 is an abundant number, since it is smaller than the sum of its proper divisors (1140333576).

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

640081944 is a wasteful number, since it uses less digits than its factorization.

640081944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240320 (or 240313 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 640081944 is about 25299.8407900129. The cubic root of 640081944 is about 861.8106542340.

The spelling of 640081944 in words is "six hundred forty million, eighty-one thousand, nine hundred forty-four".