81375881 has 4 divisors (see below), whose sum is σ = 81418512. Its totient is φ = 81333252.

The previous prime is 81375851. The next prime is 81375883. The reversal of 81375881 is 18857318.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81375881 - 2¹⁴ = 81359497 is a prime.

It is a super-3 number, since 3×81375881³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81375883) 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, 18311 + ... + 22316.

It is an arithmetic number, because the mean of its divisors is an integer number (20354628).

Almost surely, 2^81375881 is an apocalyptic number.

It is an amenable number.

81375881 is a deficient number, since it is larger than the sum of its proper divisors (42631).

81375881 is a wasteful number, since it uses less digits than its factorization.

81375881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42630.

The product of its digits is 53760, while the sum is 41.

The square root of 81375881 is about 9020.8581077412. The cubic root of 81375881 is about 433.3431152953.

The spelling of 81375881 in words is "eighty-one million, three hundred seventy-five thousand, eight hundred eighty-one".