640494863 has 4 divisors (see below), whose sum is σ = 640545480. Its totient is φ = 640444248.

The previous prime is 640494817. The next prime is 640494913. The reversal of 640494863 is 368494046.

640494863 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 25308²-1.

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 is a cyclic number.

It is not a de Polignac number, because 640494863 - 2¹⁴ = 640478479 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640494163) 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, 12653 + ... + 37961.

It is an arithmetic number, because the mean of its divisors is an integer number (160136370).

Almost surely, 2^640494863 is an apocalyptic number.

640494863 is a deficient number, since it is larger than the sum of its proper divisors (50617).

640494863 is a wasteful number, since it uses less digits than its factorization.

640494863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50616.

The product of its (nonzero) digits is 497664, while the sum is 44.

The square root of 640494863 is about 25307.9999802434. Note that the first 4 decimals coincide. The cubic root of 640494863 is about 861.9959333755.

The spelling of 640494863 in words is "six hundred forty million, four hundred ninety-four thousand, eight hundred sixty-three".