81636847 has 4 divisors (see below), whose sum is σ = 81883816. Its totient is φ = 81389880.

The previous prime is 81636829. The next prime is 81636851. The reversal of 81636847 is 74863618.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81636847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81636047) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122988 + ... + 123649.

It is an arithmetic number, because the mean of its divisors is an integer number (20470954).

Almost surely, 2^81636847 is an apocalyptic number.

81636847 is a deficient number, since it is larger than the sum of its proper divisors (246969).

81636847 is a wasteful number, since it uses less digits than its factorization.

81636847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246968.

The product of its digits is 193536, while the sum is 43.

The square root of 81636847 is about 9035.3111180523. The cubic root of 81636847 is about 433.8058533329.

The spelling of 81636847 in words is "eighty-one million, six hundred thirty-six thousand, eight hundred forty-seven".