640181256 has 128 divisors (see below), whose sum is σ = 1899555840. Its totient is φ = 177235200.

The previous prime is 640181251. The next prime is 640181263. The reversal of 640181256 is 652181046.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (640181251) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 352591 + ... + 354401.

It is an arithmetic number, because the mean of its divisors is an integer number (14840280).

Almost surely, 2^640181256 is an apocalyptic number.

640181256 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640181256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (949777920).

640181256 is an abundant number, since it is smaller than the sum of its proper divisors (1259374584).

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

640181256 is a wasteful number, since it uses less digits than its factorization.

640181256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1947 (or 1943 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 640181256 is about 25301.8034139861. The cubic root of 640181256 is about 861.8552233783.

The spelling of 640181256 in words is "six hundred forty million, one hundred eighty-one thousand, two hundred fifty-six".