81385940 has 48 divisors (see below), whose sum is σ = 177315600. Its totient is φ = 31352832.

The previous prime is 81385939. The next prime is 81385963. The reversal of 81385940 is 4958318.

81385940 is nontrivially palindromic in base 16.

It can be written as a sum of positive squares in 8 ways, for example, as 2033476 + 79352464 = 1426^2 + 8908^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81385894 and 81385903.

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, 80156 + ... + 81164.

It is an arithmetic number, because the mean of its divisors is an integer number (3694075).

Almost surely, 2^81385940 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 81385940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88657800).

81385940 is an abundant number, since it is smaller than the sum of its proper divisors (95929660).

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

81385940 is a wasteful number, since it uses less digits than its factorization.

81385940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1164 (or 1162 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 81385940 is about 9021.4156317066. The cubic root of 81385940 is about 433.3609699665.

The spelling of 81385940 in words is "eighty-one million, three hundred eighty-five thousand, nine hundred forty".