640622666 has 4 divisors (see below), whose sum is σ = 960934002. Its totient is φ = 320311332.

The previous prime is 640622659. The next prime is 640622683. The reversal of 640622666 is 666226046.

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., 613800625 + 26822041 = 24775^2 + 5179^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160155665 + ... + 160155668.

Almost surely, 2^640622666 is an apocalyptic number.

640622666 is a deficient number, since it is larger than the sum of its proper divisors (320311336).

640622666 is a wasteful number, since it uses less digits than its factorization.

640622666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320311335.

The product of its (nonzero) digits is 124416, while the sum is 38.

The square root of 640622666 is about 25310.5248068862. The cubic root of 640622666 is about 862.0532631820.

The spelling of 640622666 in words is "six hundred forty million, six hundred twenty-two thousand, six hundred sixty-six".