81387447 has 4 divisors (see below), whose sum is σ = 108516600. Its totient is φ = 54258296.

The previous prime is 81387443. The next prime is 81387473. The reversal of 81387447 is 74478318.

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 81387447 - 2² = 81387443 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81387399 and 81387408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81387443) 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, 13564572 + ... + 13564577.

It is an arithmetic number, because the mean of its divisors is an integer number (27129150).

Almost surely, 2^81387447 is an apocalyptic number.

81387447 is a deficient number, since it is larger than the sum of its proper divisors (27129153).

81387447 is a wasteful number, since it uses less digits than its factorization.

81387447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27129152.

The product of its digits is 150528, while the sum is 42.

The square root of 81387447 is about 9021.4991547968. The cubic root of 81387447 is about 433.3636447567.

The spelling of 81387447 in words is "eighty-one million, three hundred eighty-seven thousand, four hundred forty-seven".