81219866 has 16 divisors (see below), whose sum is σ = 149944704. Its totient is φ = 32130864.

The previous prime is 81219841. The next prime is 81219871. The reversal of 81219866 is 66891218.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 222950 + ... + 223313.

It is an arithmetic number, because the mean of its divisors is an integer number (9371544).

Almost surely, 2^81219866 is an apocalyptic number.

81219866 is a deficient number, since it is larger than the sum of its proper divisors (68724838).

81219866 is a wasteful number, since it uses less digits than its factorization.

81219866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446285.

The product of its digits is 41472, while the sum is 41.

The square root of 81219866 is about 9012.2065000753. The cubic root of 81219866 is about 433.0660009229.

The spelling of 81219866 in words is "eighty-one million, two hundred nineteen thousand, eight hundred sixty-six".