640665206 has 4 divisors (see below), whose sum is σ = 960997812. Its totient is φ = 320332602.

The previous prime is 640665203. The next prime is 640665209. The reversal of 640665206 is 602566046.

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

It is an interprime number because it is at equal distance from previous prime (640665203) and next prime (640665209).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640665203) by changing a digit.

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, 160166300 + ... + 160166303.

It is an arithmetic number, because the mean of its divisors is an integer number (240249453).

Almost surely, 2^640665206 is an apocalyptic number.

640665206 is a deficient number, since it is larger than the sum of its proper divisors (320332606).

640665206 is a wasteful number, since it uses less digits than its factorization.

640665206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320332605.

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 640665206 is about 25311.3651548074. The cubic root of 640665206 is about 862.0723440628.

Adding to 640665206 its product of nonzero digits (51840), we get a palindrome (640717046).

The spelling of 640665206 in words is "six hundred forty million, six hundred sixty-five thousand, two hundred six".