393934921 has 2 divisors, whose sum is σ = 393934922. Its totient is φ = 393934920.

The previous prime is 393934907. The next prime is 393934963. The reversal of 393934921 is 129439393.

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., 315417600 + 78517321 = 17760^2 + 8861^2 .

It is an emirp because it is prime and its reverse (129439393) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 393934921 - 2¹⁷ = 393803849 is a prime.

It is not a weakly prime, because it can be changed into another prime (393934721) 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, 196967460 + 196967461.

It is an arithmetic number, because the mean of its divisors is an integer number (196967461).

Almost surely, 2^393934921 is an apocalyptic number.

It is an amenable number.

393934921 is a deficient number, since it is larger than the sum of its proper divisors (1).

393934921 is an equidigital number, since it uses as much as digits as its factorization.

393934921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 157464, while the sum is 43.

The square root of 393934921 is about 19847.7938572528. The cubic root of 393934921 is about 733.0633272975.

The spelling of 393934921 in words is "three hundred ninety-three million, nine hundred thirty-four thousand, nine hundred twenty-one".