399920009 has 2 divisors, whose sum is σ = 399920010. Its totient is φ = 399920008.

The previous prime is 399919981. The next prime is 399920029. The reversal of 399920009 is 900029993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 399880009 + 40000 = 19997^2 + 200^2 .

It is a cyclic number.

It is not a de Polignac number, because 399920009 - 2¹² = 399915913 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (399920029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199960004 + 199960005.

It is an arithmetic number, because the mean of its divisors is an integer number (199960005).

Almost surely, 2^399920009 is an apocalyptic number.

It is an amenable number.

399920009 is a deficient number, since it is larger than the sum of its proper divisors (1).

399920009 is an equidigital number, since it uses as much as digits as its factorization.

399920009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 39366, while the sum is 41.

The square root of 399920009 is about 19998.0001250125. Note that the first 3 decimals coincide. The cubic root of 399920009 is about 736.7571815598.

The spelling of 399920009 in words is "three hundred ninety-nine million, nine hundred twenty thousand, nine".