393943681 has 2 divisors, whose sum is σ = 393943682. Its totient is φ = 393943680.

The previous prime is 393943657. The next prime is 393943717. The reversal of 393943681 is 186349393.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 331786225 + 62157456 = 18215^2 + 7884^2 .

It is a cyclic number.

It is not a de Polignac number, because 393943681 - 2¹³ = 393935489 is a prime.

It is a super-2 number, since 2×393943681² = 310383247599659522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (391943681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 196971840 + 196971841.

It is an arithmetic number, because the mean of its divisors is an integer number (196971841).

Almost surely, 2^393943681 is an apocalyptic number.

It is an amenable number.

393943681 is a deficient number, since it is larger than the sum of its proper divisors (1).

393943681 is an equidigital number, since it uses as much as digits as its factorization.

393943681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 419904, while the sum is 46.

The square root of 393943681 is about 19848.0145354642. The cubic root of 393943681 is about 733.0687610098.

The spelling of 393943681 in words is "three hundred ninety-three million, nine hundred forty-three thousand, six hundred eighty-one".