81005371 has 4 divisors (see below), whose sum is σ = 81023544. Its totient is φ = 80987200.

The previous prime is 81005369. The next prime is 81005383. The reversal of 81005371 is 17350018.

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 81005371 - 2¹ = 81005369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81005311) 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, 2676 + ... + 13006.

It is an arithmetic number, because the mean of its divisors is an integer number (20255886).

Almost surely, 2^81005371 is an apocalyptic number.

81005371 is a deficient number, since it is larger than the sum of its proper divisors (18173).

81005371 is a wasteful number, since it uses less digits than its factorization.

81005371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18172.

The product of its (nonzero) digits is 840, while the sum is 25.

The square root of 81005371 is about 9000.2983839426. The cubic root of 81005371 is about 432.6844342419.

Adding to 81005371 its reverse (17350018), we get a palindrome (98355389).

The spelling of 81005371 in words is "eighty-one million, five thousand, three hundred seventy-one".