399366421 has 2 divisors, whose sum is σ = 399366422. Its totient is φ = 399366420.

The previous prime is 399366389. The next prime is 399366439. The reversal of 399366421 is 124663993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 335988900 + 63377521 = 18330^2 + 7961^2 .

It is an emirp because it is prime and its reverse (124663993) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 399366421 - 2⁵ = 399366389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399366481) 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, 199683210 + 199683211.

It is an arithmetic number, because the mean of its divisors is an integer number (199683211).

Almost surely, 2^399366421 is an apocalyptic number.

It is an amenable number.

399366421 is a deficient number, since it is larger than the sum of its proper divisors (1).

399366421 is an equidigital number, since it uses as much as digits as its factorization.

399366421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 209952, while the sum is 43.

The square root of 399366421 is about 19984.1542478034. The cubic root of 399366421 is about 736.4170733188.

The spelling of 399366421 in words is "three hundred ninety-nine million, three hundred sixty-six thousand, four hundred twenty-one".