81090999808 has 160 divisors (see below), whose sum is σ = 201947074560. Its totient is φ = 31672442880.

The previous prime is 81090999799. The next prime is 81090999827. The reversal of 81090999808 is 80899909018.

It is a super-2 number, since 2×81090999808² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3669753 + ... + 3691783.

It is an arithmetic number, because the mean of its divisors is an integer number (1262169216).

Almost surely, 2^81090999808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81090999808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100973537280).

81090999808 is an abundant number, since it is smaller than the sum of its proper divisors (120856074752).

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

81090999808 is a wasteful number, since it uses less digits than its factorization.

81090999808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22148 (or 22132 counting only the distinct ones).

The product of its (nonzero) digits is 3359232, while the sum is 61.

The spelling of 81090999808 in words is "eighty-one billion, ninety million, nine hundred ninety-nine thousand, eight hundred eight".