81909144 has 80 divisors (see below), whose sum is σ = 235093320. Its totient is φ = 26628480.

The previous prime is 81909127. The next prime is 81909151. The reversal of 81909144 is 44190918.

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 = 81909099 and 81909108.

It is a congruent number.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 25027 + ... + 28109.

Almost surely, 2^81909144 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 81909144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117546660).

81909144 is an abundant number, since it is smaller than the sum of its proper divisors (153184176).

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

81909144 is a wasteful number, since it uses less digits than its factorization.

81909144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3142 (or 3129 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 81909144 is about 9050.3670643792. The cubic root of 81909144 is about 434.2876330957.

It can be divided in two parts, 8190914 and 4, that added together give a palindrome (8190918).

The spelling of 81909144 in words is "eighty-one million, nine hundred nine thousand, one hundred forty-four".