81281844 has 72 divisors (see below), whose sum is σ = 240571968. Its totient is φ = 22654080.

The previous prime is 81281833. The next prime is 81281869. The reversal of 81281844 is 44818218.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 81281799 and 81281808.

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 23 ways as a sum of consecutive naturals, for example, 6399 + ... + 14265.

Almost surely, 2^81281844 is an apocalyptic number.

81281844 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81281844, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (120285984).

81281844 is an abundant number, since it is smaller than the sum of its proper divisors (159290124).

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

81281844 is a wasteful number, since it uses less digits than its factorization.

81281844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7925 (or 7920 counting only the distinct ones).

The product of its digits is 16384, while the sum is 36.

The square root of 81281844 is about 9015.6444029254. The cubic root of 81281844 is about 433.1761289067.

The spelling of 81281844 in words is "eighty-one million, two hundred eighty-one thousand, eight hundred forty-four".