81443825 has 6 divisors (see below), whose sum is σ = 100990374. Its totient is φ = 65155040.

The previous prime is 81443779. The next prime is 81443827. The reversal of 81443825 is 52834418.

It can be written as a sum of positive squares in 3 ways, for example, as 4986289 + 76457536 = 2233^2 + 8744^2 .

It is not a de Polignac number, because 81443825 - 2¹⁶ = 81378289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81443827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1628852 + ... + 1628901.

It is an arithmetic number, because the mean of its divisors is an integer number (16831729).

Almost surely, 2^81443825 is an apocalyptic number.

It is an amenable number.

81443825 is a deficient number, since it is larger than the sum of its proper divisors (19546549).

81443825 is a wasteful number, since it uses less digits than its factorization.

81443825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3257763 (or 3257758 counting only the distinct ones).

The product of its digits is 30720, while the sum is 35.

The square root of 81443825 is about 9024.6232608348. The cubic root of 81443825 is about 433.4636869506.

The spelling of 81443825 in words is "eighty-one million, four hundred forty-three thousand, eight hundred twenty-five".