81815347 has 4 divisors (see below), whose sum is σ = 85372560. Its totient is φ = 78258136.

The previous prime is 81815309. The next prime is 81815381. The reversal of 81815347 is 74351818.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81815347 - 2¹⁵ = 81782579 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81815947) 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 3 ways as a sum of consecutive naturals, for example, 1778572 + ... + 1778617.

It is an arithmetic number, because the mean of its divisors is an integer number (21343140).

Almost surely, 2^81815347 is an apocalyptic number.

81815347 is a deficient number, since it is larger than the sum of its proper divisors (3557213).

81815347 is a wasteful number, since it uses less digits than its factorization.

81815347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3557212.

The product of its digits is 26880, while the sum is 37.

The square root of 81815347 is about 9045.1836355046. The cubic root of 81815347 is about 434.1217971706.

The spelling of 81815347 in words is "eighty-one million, eight hundred fifteen thousand, three hundred forty-seven".