400000009 has 2 divisors, whose sum is σ = 400000010. Its totient is φ = 400000008.

The previous prime is 399999959. The next prime is 400000043. The reversal of 400000009 is 900000004.

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., 400000000 + 9 = 20000^2 + 3^2 .

It is a cyclic number.

It is not a de Polignac number, because 400000009 - 2⁹ = 399999497 is a prime.

400000009 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 (400000049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200000004 + 200000005.

It is an arithmetic number, because the mean of its divisors is an integer number (200000005).

Almost surely, 2^400000009 is an apocalyptic number.

It is an amenable number.

400000009 is a deficient number, since it is larger than the sum of its proper divisors (1).

400000009 is an equidigital number, since it uses as much as digits as its factorization.

400000009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 400000009 is about 20000.0002250000. Note that the first 3 decimals coincide. The cubic root of 400000009 is about 736.8063052541.

The spelling of 400000009 in words is "four hundred million, nine", and thus it is an aban number.