81506005 has 16 divisors (see below), whose sum is σ = 114802560. Its totient is φ = 54378432.

The previous prime is 81505999. The next prime is 81506053. The reversal of 81506005 is 50060518.

It is a cyclic number.

It is not a de Polignac number, because 81506005 - 2¹⁵ = 81473237 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 (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30175 + ... + 32764.

It is an arithmetic number, because the mean of its divisors is an integer number (7175160).

Almost surely, 2^81506005 is an apocalyptic number.

It is an amenable number.

81506005 is a deficient number, since it is larger than the sum of its proper divisors (33296555).

81506005 is a wasteful number, since it uses less digits than its factorization.

81506005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62988.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 81506005 is about 9028.0676226976. The cubic root of 81506005 is about 433.5739712099.

The spelling of 81506005 in words is "eighty-one million, five hundred six thousand, five".