81813908 has 36 divisors (see below), whose sum is σ = 158731776. Its totient is φ = 36895320.

The previous prime is 81813899. The next prime is 81813913. The reversal of 81813908 is 80931818.

It is a nialpdrome in base 11.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 644141 + ... + 644267.

It is an arithmetic number, because the mean of its divisors is an integer number (4409216).

Almost surely, 2^81813908 is an apocalyptic number.

It is an amenable number.

81813908 is a deficient number, since it is larger than the sum of its proper divisors (76917868).

81813908 is an equidigital number, since it uses as much as digits as its factorization.

81813908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 38.

The square root of 81813908 is about 9045.1040900589. The cubic root of 81813908 is about 434.1192519883.

The spelling of 81813908 in words is "eighty-one million, eight hundred thirteen thousand, nine hundred eight".