81188381 has 8 divisors (see below), whose sum is σ = 82590840. Its totient is φ = 79796992.

The previous prime is 81188351. The next prime is 81188383. The reversal of 81188381 is 18388118.

It can be written as a sum of positive squares in 4 ways, for example, as 16240900 + 64947481 = 4030^2 + 8059^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81188381 is a prime.

It is a super-3 number, since 3×81188381³ (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 a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81188383) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12761 + ... + 18033.

It is an arithmetic number, because the mean of its divisors is an integer number (10323855).

Almost surely, 2^81188381 is an apocalyptic number.

It is an amenable number.

81188381 is a deficient number, since it is larger than the sum of its proper divisors (1402459).

81188381 is a wasteful number, since it uses less digits than its factorization.

81188381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5535.

The product of its digits is 12288, while the sum is 38.

The square root of 81188381 is about 9010.4595332314. The cubic root of 81188381 is about 433.0100341339.

The spelling of 81188381 in words is "eighty-one million, one hundred eighty-eight thousand, three hundred eighty-one".