40005 has 24 divisors (see below), whose sum is σ = 79872. Its totient is φ = 18144.

The previous prime is 39989. The next prime is 40009. The reversal of 40005 is 50004.

It is not a de Polignac number, because 40005 - 2⁴ = 39989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an Ulam number.

40005 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (40009) 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 23 ways as a sum of consecutive naturals, for example, 252 + ... + 378.

It is an arithmetic number, because the mean of its divisors is an integer number (3328).

2⁴⁰⁰⁰⁵ is an apocalyptic number.

40005 is a gapful number since it is divisible by the number (45) formed by its first and last digit.

It is an amenable number.

40005 is a deficient number, since it is larger than the sum of its proper divisors (39867).

40005 is a wasteful number, since it uses less digits than its factorization.

40005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 9.

The square root of 40005 is about 200.0124996094. The cubic root of 40005 is about 34.2009438541.

Adding to 40005 its reverse (50004), we get a palindrome (90009).

Subtracting 40005 from its reverse (50004), we obtain a palindrome (9999).

It can be divided in two parts, 4000 and 5, that added together give a triangular number (4005 = T₈₉).

The spelling of 40005 in words is "forty thousand, five".