81861105 has 16 divisors (see below), whose sum is σ = 132773760. Its totient is φ = 43060608.

The previous prime is 81861079. The next prime is 81861107. The reversal of 81861105 is 50116818.

It is a happy number.

It is not a de Polignac number, because 81861105 - 2⁶ = 81861041 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81861107) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 36285 + ... + 38474.

It is an arithmetic number, because the mean of its divisors is an integer number (8298360).

Almost surely, 2^81861105 is an apocalyptic number.

It is an amenable number.

81861105 is a deficient number, since it is larger than the sum of its proper divisors (50912655).

81861105 is a wasteful number, since it uses less digits than its factorization.

81861105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74840.

The product of its (nonzero) digits is 1920, while the sum is 30.

The square root of 81861105 is about 9047.7126943775. The cubic root of 81861105 is about 434.2027145199.

The spelling of 81861105 in words is "eighty-one million, eight hundred sixty-one thousand, one hundred five".