40009 has 2 divisors, whose sum is σ = 40010.
Its totient is φ = 40008.
The previous prime is 39989. The next prime is 40013. The reversal of 40009 is 90004.
It is a happy number.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 40000 + 9 = 200^2 + 3^2
It is a cyclic number.
It is not a de Polignac number, because 40009 - 213 = 31817 is a prime.
It is a Chen prime.
40009 is a modest number, since divided by 9 gives 4 as remainder.
It is not a weakly prime, because it can be changed into another prime (40039) 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 as a sum of consecutive naturals, namely, 20004 + 20005.
It is an arithmetic number, because the mean of its divisors is an integer number (20005).
240009 is an apocalyptic number.
It is an amenable number.
40009 is a deficient number, since it is larger than the sum of its proper divisors (1).
40009 is an equidigital number, since it uses as much as digits as its factorization.
40009 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 36, while the sum is 13.
The square root of 40009 is about 200.0224987345.
The cubic root of 40009 is about 34.2020837051.
The spelling of 40009 in words is "forty thousand, nine".