640826818 has 4 divisors (see below), whose sum is σ = 961240230. Its totient is φ = 320413408.

The previous prime is 640826803. The next prime is 640826819. The reversal of 640826818 is 818628046.

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., 631868769 + 8958049 = 25137^2 + 2993^2 .

It is not an unprimeable number, because it can be changed into a prime (640826819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160206703 + ... + 160206706.

Almost surely, 2^640826818 is an apocalyptic number.

640826818 is a deficient number, since it is larger than the sum of its proper divisors (320413412).

640826818 is a wasteful number, since it uses less digits than its factorization.

640826818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320413411.

The product of its (nonzero) digits is 147456, while the sum is 43.

The square root of 640826818 is about 25314.5574324340. The cubic root of 640826818 is about 862.1448257694.

The spelling of 640826818 in words is "six hundred forty million, eight hundred twenty-six thousand, eight hundred eighteen".