400191809 has 2 divisors, whose sum is σ = 400191810. Its totient is φ = 400191808.

The previous prime is 400191797. The next prime is 400191811. The reversal of 400191809 is 908191004.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 398880784 + 1311025 = 19972^2 + 1145^2 .

It is a cyclic number.

It is not a de Polignac number, because 400191809 - 2¹⁶ = 400126273 is a prime.

Together with 400191811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (400191829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200095904 + 200095905.

It is an arithmetic number, because the mean of its divisors is an integer number (200095905).

Almost surely, 2^400191809 is an apocalyptic number.

It is an amenable number.

400191809 is a deficient number, since it is larger than the sum of its proper divisors (1).

400191809 is an equidigital number, since it uses as much as digits as its factorization.

400191809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 400191809 is about 20004.7946502832. The cubic root of 400191809 is about 736.9240526413.

The spelling of 400191809 in words is "four hundred million, one hundred ninety-one thousand, eight hundred nine".