398777809 has 2 divisors, whose sum is σ = 398777810. Its totient is φ = 398777808.

The previous prime is 398777783. The next prime is 398777837. The reversal of 398777809 is 908777893.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 397404225 + 1373584 = 19935^2 + 1172^2 .

It is a cyclic number.

It is not a de Polignac number, because 398777809 - 2¹⁷ = 398646737 is a prime.

It is not a weakly prime, because it can be changed into another prime (398777839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199388904 + 199388905.

It is an arithmetic number, because the mean of its divisors is an integer number (199388905).

Almost surely, 2^398777809 is an apocalyptic number.

It is an amenable number.

398777809 is a deficient number, since it is larger than the sum of its proper divisors (1).

398777809 is an equidigital number, since it uses as much as digits as its factorization.

398777809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5334336, while the sum is 58.

The square root of 398777809 is about 19969.4218494177. The cubic root of 398777809 is about 736.0551024287.

It can be divided in two parts, 3987 and 77809, that added together give a square (81796 = 286²).

The spelling of 398777809 in words is "three hundred ninety-eight million, seven hundred seventy-seven thousand, eight hundred nine".