81939144 has 32 divisors (see below), whose sum is σ = 234112320. Its totient is φ = 23411136.

The previous prime is 81939139. The next prime is 81939149. The reversal of 81939144 is 44193918.

It is an interprime number because it is at equal distance from previous prime (81939139) and next prime (81939149).

It is not an unprimeable number, because it can be changed into a prime (81939149) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 243699 + ... + 244034.

It is an arithmetic number, because the mean of its divisors is an integer number (7316010).

Almost surely, 2^81939144 is an apocalyptic number.

81939144 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

81939144 is an abundant number, since it is smaller than the sum of its proper divisors (152173176).

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

81939144 is a wasteful number, since it uses less digits than its factorization.

81939144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487749 (or 487745 counting only the distinct ones).

The product of its digits is 31104, while the sum is 39.

The square root of 81939144 is about 9052.0243039886. The cubic root of 81939144 is about 434.3406472772.

It can be divided in two parts, 8193914 and 4, that added together give a palindrome (8193918).

The spelling of 81939144 in words is "eighty-one million, nine hundred thirty-nine thousand, one hundred forty-four".