399355681 has 2 divisors, whose sum is σ = 399355682. Its totient is φ = 399355680.

The previous prime is 399355679. The next prime is 399355741. The reversal of 399355681 is 186553993.

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., 221533456 + 177822225 = 14884^2 + 13335^2 .

It is a cyclic number.

It is not a de Polignac number, because 399355681 - 2¹ = 399355679 is a prime.

It is a super-2 number, since 2×399355681² = 318969919893947522, which contains 22 as substring.

Together with 399355679, 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 (399355631) 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, 199677840 + 199677841.

It is an arithmetic number, because the mean of its divisors is an integer number (199677841).

Almost surely, 2^399355681 is an apocalyptic number.

It is an amenable number.

399355681 is a deficient number, since it is larger than the sum of its proper divisors (1).

399355681 is an equidigital number, since it uses as much as digits as its factorization.

399355681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 874800, while the sum is 49.

The square root of 399355681 is about 19983.8855330989. The cubic root of 399355681 is about 736.4104718706.

The spelling of 399355681 in words is "three hundred ninety-nine million, three hundred fifty-five thousand, six hundred eighty-one".