640306813 has 16 divisors (see below), whose sum is σ = 661513216. Its totient is φ = 619539840.

The previous prime is 640306811. The next prime is 640306861. The reversal of 640306813 is 318603046.

It is a cyclic number.

It is not a de Polignac number, because 640306813 - 2¹ = 640306811 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 (640306811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1400881 + ... + 1401337.

It is an arithmetic number, because the mean of its divisors is an integer number (41344576).

Almost surely, 2^640306813 is an apocalyptic number.

It is an amenable number.

640306813 is a deficient number, since it is larger than the sum of its proper divisors (21206403).

640306813 is a wasteful number, since it uses less digits than its factorization.

640306813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844.

The product of its (nonzero) digits is 10368, while the sum is 31.

The square root of 640306813 is about 25304.2844791154. The cubic root of 640306813 is about 861.9115641316.

Adding to 640306813 its reverse (318603046), we get a palindrome (958909859).

The spelling of 640306813 in words is "six hundred forty million, three hundred six thousand, eight hundred thirteen".