81999145 has 8 divisors (see below), whose sum is σ = 98457480. Its totient is φ = 65560320.

The previous prime is 81999133. The next prime is 81999167. The reversal of 81999145 is 54199918.

It can be written as a sum of positive squares in 4 ways, for example, as 205209 + 81793936 = 453^2 + 9044^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-81999145 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81999095 and 81999104.

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, 7011 + ... + 14599.

It is an arithmetic number, because the mean of its divisors is an integer number (12307185).

Almost surely, 2^81999145 is an apocalyptic number.

It is an amenable number.

81999145 is a deficient number, since it is larger than the sum of its proper divisors (16458335).

81999145 is a wasteful number, since it uses less digits than its factorization.

81999145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9755.

The product of its digits is 116640, while the sum is 46.

The square root of 81999145 is about 9055.3379285370. The cubic root of 81999145 is about 434.4466385994.

The spelling of 81999145 in words is "eighty-one million, nine hundred ninety-nine thousand, one hundred forty-five".