640081943 has 4 divisors (see below), whose sum is σ = 677733840. Its totient is φ = 602430048.

The previous prime is 640081931. The next prime is 640081963. The reversal of 640081943 is 349180046.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640081943 - 2¹² = 640077847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640081963) 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 3 ways as a sum of consecutive naturals, for example, 18825923 + ... + 18825956.

It is an arithmetic number, because the mean of its divisors is an integer number (169433460).

Almost surely, 2^640081943 is an apocalyptic number.

640081943 is a deficient number, since it is larger than the sum of its proper divisors (37651897).

640081943 is a wasteful number, since it uses less digits than its factorization.

640081943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37651896.

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 640081943 is about 25299.8407702499. The cubic root of 640081943 is about 861.8106537852.

The spelling of 640081943 in words is "six hundred forty million, eighty-one thousand, nine hundred forty-three".