640400186 has 4 divisors (see below), whose sum is σ = 960600282. Its totient is φ = 320200092.

The previous prime is 640400177. The next prime is 640400203. The reversal of 640400186 is 681004046.

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

It can be written as a sum of positive squares in only one way, i.e., 634788025 + 5612161 = 25195^2 + 2369^2 .

It is a super-2 number, since 2×640400186² = 820224796457669192, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160100045 + ... + 160100048.

Almost surely, 2^640400186 is an apocalyptic number.

640400186 is a deficient number, since it is larger than the sum of its proper divisors (320200096).

640400186 is a wasteful number, since it uses less digits than its factorization.

640400186 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320200095.

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 640400186 is about 25306.1294156179. The cubic root of 640400186 is about 861.9534582961.

The spelling of 640400186 in words is "six hundred forty million, four hundred thousand, one hundred eighty-six".