640896181 has 4 divisors (see below), whose sum is σ = 640962700. Its totient is φ = 640829664.

The previous prime is 640896131. The next prime is 640896199. The reversal of 640896181 is 181698046.

640896181 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 430936081 + 209960100 = 20759^2 + 14490^2 .

It is a cyclic number.

It is not a de Polignac number, because 640896181 - 2¹⁵ = 640863413 is a prime.

It is a super-2 number, since 2×640896181² = 821495829640769522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640896101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15726 + ... + 39103.

It is an arithmetic number, because the mean of its divisors is an integer number (160240675).

Almost surely, 2^640896181 is an apocalyptic number.

It is an amenable number.

640896181 is a deficient number, since it is larger than the sum of its proper divisors (66519).

640896181 is a wasteful number, since it uses less digits than its factorization.

640896181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66518.

The product of its (nonzero) digits is 82944, while the sum is 43.

The square root of 640896181 is about 25315.9274173395. The cubic root of 640896181 is about 862.1759307899.

The spelling of 640896181 in words is "six hundred forty million, eight hundred ninety-six thousand, one hundred eighty-one".