8191991808 has 896 divisors, whose sum is σ = 33468503040. Its totient is φ = 1911029760.

The previous prime is 8191991789. The next prime is 8191991809. The reversal of 8191991808 is 8081991918.

It is a tau number, because it is divible by the number of its divisors (896).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8191991809) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 221405166 + ... + 221405202.

It is an arithmetic number, because the mean of its divisors is an integer number (37353240).

Almost surely, 2^8191991808 is an apocalyptic number.

8191991808 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 8191991808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16734251520).

8191991808 is an abundant number, since it is smaller than the sum of its proper divisors (25276511232).

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

8191991808 is a wasteful number, since it uses less digits than its factorization.

8191991808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 54.

The square root of 8191991808 is about 90509.6227370328. The cubic root of 8191991808 is about 2015.8730078737.

It can be divided in two parts, 8191 and 991808, that added together give a palindrome (999999).

The spelling of 8191991808 in words is "eight billion, one hundred ninety-one million, nine hundred ninety-one thousand, eight hundred eight".