81940 has 24 divisors (see below), whose sum is σ = 182952. Its totient is φ = 30720.

The previous prime is 81937. The next prime is 81943. The reversal of 81940 is 4918.

81940 = T₁₁ + T₁₂ + ... + T₇₈.

It is an interprime number because it is at equal distance from previous prime (81937) and next prime (81943).

It can be written as a sum of positive squares in 4 ways, for example, as 26244 + 55696 = 162^2 + 236^2 .

It is a hoax number, since the sum of its digits (22) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81943) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 220 + ... + 460.

It is an arithmetic number, because the mean of its divisors is an integer number (7623).

2⁸¹⁹⁴⁰ 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 81940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (91476).

81940 is an abundant number, since it is smaller than the sum of its proper divisors (101012).

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

81940 is a wasteful number, since it uses less digits than its factorization.

81940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267 (or 265 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 81940 is about 286.2516375499. The cubic root of 81940 is about 43.4342159759.

Subtracting from 81940 its sum of digits (22), we obtain a palindrome (81918).

Adding to 81940 its product of nonzero digits (288), we get a palindrome (82228).

The spelling of 81940 in words is "eighty-one thousand, nine hundred forty".