813331638 has 64 divisors (see below), whose sum is σ = 2100672000. Its totient is φ = 228435552.

The previous prime is 813331633. The next prime is 813331733. The reversal of 813331638 is 836133318.

813331638 is a `hidden beast` number, since 8 + 13 + 3 + 3 + 1 + 638 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (813331633) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4068 + ... + 40536.

It is an arithmetic number, because the mean of its divisors is an integer number (32823000).

Almost surely, 2^813331638 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 813331638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1050336000).

813331638 is an abundant number, since it is smaller than the sum of its proper divisors (1287340362).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

813331638 is a wasteful number, since it uses less digits than its factorization.

813331638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36546 (or 36540 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 813331638 is about 28518.9697920524. The cubic root of 813331638 is about 933.4460496806.

The spelling of 813331638 in words is "eight hundred thirteen million, three hundred thirty-one thousand, six hundred thirty-eight".