40081 has 4 divisors (see below), whose sum is σ = 40500. Its totient is φ = 39664.

The previous prime is 40063. The next prime is 40087. The reversal of 40081 is 18004.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 3600 + 36481 = 60^2 + 191^2 .

It is a cyclic number.

It is not a de Polignac number, because 40081 - 2⁷ = 39953 is a prime.

It is a super-2 number, since 2×40081² = 3212973122, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (40087) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15 + ... + 283.

It is an arithmetic number, because the mean of its divisors is an integer number (10125).

2⁴⁰⁰⁸¹ is an apocalyptic number.

It is an amenable number.

40081 is a deficient number, since it is larger than the sum of its proper divisors (419).

40081 is a wasteful number, since it uses less digits than its factorization.

With its successor (40082) it forms a Ruth-Aaron pair, since the sum of their distinct prime factors is the same (418).

40081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 40081 is about 200.2023975880. The cubic root of 40081 is about 34.2225880442. Note that the first 3 decimals are identical.

Adding to 40081 its reverse (18004), we get a palindrome (58085).

It can be divided in two parts, 400 and 81, that multiplied together give a square (32400 = 180²).

The spelling of 40081 in words is "forty thousand, eighty-one".