640081091 has 8 divisors (see below), whose sum is σ = 689592624. Its totient is φ = 590608800.

The previous prime is 640081073. The next prime is 640081097. The reversal of 640081091 is 190180046.

640081091 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640081091 - 2¹⁴ = 640064707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640081097) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30116 + ... + 46766.

It is an arithmetic number, because the mean of its divisors is an integer number (86199078).

Almost surely, 2^640081091 is an apocalyptic number.

640081091 is a deficient number, since it is larger than the sum of its proper divisors (49511533).

640081091 is a wasteful number, since it uses less digits than its factorization.

640081091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19621.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 640081091 is about 25299.8239321937. The cubic root of 640081091 is about 861.8102714055.

The spelling of 640081091 in words is "six hundred forty million, eighty-one thousand, ninety-one".