399622721 has 2 divisors, whose sum is σ = 399622722. Its totient is φ = 399622720.

The previous prime is 399622711. The next prime is 399622747. The reversal of 399622721 is 127226993.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 276856321 + 122766400 = 16639^2 + 11080^2 .

It is an emirp because it is prime and its reverse (127226993) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-399622721 is a prime.

It is not a weakly prime, because it can be changed into another prime (399622711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199811360 + 199811361.

It is an arithmetic number, because the mean of its divisors is an integer number (199811361).

Almost surely, 2^399622721 is an apocalyptic number.

It is an amenable number.

399622721 is a deficient number, since it is larger than the sum of its proper divisors (1).

399622721 is an equidigital number, since it uses as much as digits as its factorization.

399622721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 81648, while the sum is 41.

The square root of 399622721 is about 19990.5657998967. The cubic root of 399622721 is about 736.5745755723.

The spelling of 399622721 in words is "three hundred ninety-nine million, six hundred twenty-two thousand, seven hundred twenty-one".