81306288 has 240 divisors, whose sum is σ = 284981760. Its totient is φ = 22087296.

The previous prime is 81306271. The next prime is 81306299. The reversal of 81306288 is 88260318.

It is a Cunningham number, because it is equal to 9017²-1.

It is a super-2 number, since 2×81306288² = 13221424936677888, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 486781 + ... + 486947.

It is an arithmetic number, because the mean of its divisors is an integer number (1187424).

Almost surely, 2^81306288 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81306288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142490880).

81306288 is an abundant number, since it is smaller than the sum of its proper divisors (203675472).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81306288 is a wasteful number, since it uses less digits than its factorization.

81306288 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221 (or 202 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 81306288 is about 9016.9999445492. Note that the first 4 decimals coincide. The cubic root of 81306288 is about 433.2195477709.

The spelling of 81306288 in words is "eighty-one million, three hundred six thousand, two hundred eighty-eight".