81820208 has 20 divisors (see below), whose sum is σ = 158687760. Its totient is φ = 40868544.

The previous prime is 81820183. The next prime is 81820217. The reversal of 81820208 is 80202818.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19166 + ... + 23042.

It is an arithmetic number, because the mean of its divisors is an integer number (7934388).

Almost surely, 2^81820208 is an apocalyptic number.

It is an amenable number.

81820208 is a deficient number, since it is larger than the sum of its proper divisors (76867552).

81820208 is a wasteful number, since it uses less digits than its factorization.

81820208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5204 (or 5198 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 29.

The square root of 81820208 is about 9045.4523380536. The cubic root of 81820208 is about 434.1303946785.

It can be divided in two parts, 81820 and 208, that added together give a palindrome (82028).

The spelling of 81820208 in words is "eighty-one million, eight hundred twenty thousand, two hundred eight".