399781819 has 2 divisors, whose sum is σ = 399781820. Its totient is φ = 399781818.

The previous prime is 399781813. The next prime is 399781873. The reversal of 399781819 is 918187993.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 399781819 - 2⁹ = 399781307 is a prime.

It is a super-2 number, since 2×399781819² = 319651005605897522, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 399781819.

It is not a weakly prime, because it can be changed into another prime (399781813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199890909 + 199890910.

It is an arithmetic number, because the mean of its divisors is an integer number (199890910).

Almost surely, 2^399781819 is an apocalyptic number.

399781819 is a deficient number, since it is larger than the sum of its proper divisors (1).

399781819 is an equidigital number, since it uses as much as digits as its factorization.

399781819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 979776, while the sum is 55.

The square root of 399781819 is about 19994.5447310010. The cubic root of 399781819 is about 736.6723110842.

The spelling of 399781819 in words is "three hundred ninety-nine million, seven hundred eighty-one thousand, eight hundred nineteen".