81491228 has 48 divisors (see below), whose sum is σ = 184773120. Its totient is φ = 30538944.

The previous prime is 81491203. The next prime is 81491237. The reversal of 81491228 is 82219418.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1025 + ... + 12807.

It is an arithmetic number, because the mean of its divisors is an integer number (3849440).

Almost surely, 2^81491228 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 81491228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92386560).

81491228 is an abundant number, since it is smaller than the sum of its proper divisors (103281892).

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

81491228 is a wasteful number, since it uses less digits than its factorization.

81491228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11826 (or 11824 counting only the distinct ones).

The product of its digits is 9216, while the sum is 35.

The square root of 81491228 is about 9027.2491934143. The cubic root of 81491228 is about 433.5477673746.

The spelling of 81491228 in words is "eighty-one million, four hundred ninety-one thousand, two hundred twenty-eight".