81861845 has 8 divisors (see below), whose sum is σ = 105790776. Its totient is φ = 60451776.

The previous prime is 81861803. The next prime is 81861869. The reversal of 81861845 is 54816818.

It can be written as a sum of positive squares in 4 ways, for example, as 18722929 + 63138916 = 4327^2 + 7946^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81861845 - 2¹⁴ = 81845461 is a prime.

It is a congruent 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, 629642 + ... + 629771.

It is an arithmetic number, because the mean of its divisors is an integer number (13223847).

Almost surely, 2^81861845 is an apocalyptic number.

It is an amenable number.

81861845 is a deficient number, since it is larger than the sum of its proper divisors (23928931).

81861845 is a wasteful number, since it uses less digits than its factorization.

81861845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1259431.

The product of its digits is 61440, while the sum is 41.

The square root of 81861845 is about 9047.7535885987. The cubic root of 81861845 is about 434.2040228704.

The spelling of 81861845 in words is "eighty-one million, eight hundred sixty-one thousand, eight hundred forty-five".