6443981 has 2 divisors, whose sum is σ = 6443982. Its totient is φ = 6443980.

The previous prime is 6443977. The next prime is 6443999. The reversal of 6443981 is 1893446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4268356 + 2175625 = 2066^2 + 1475^2 .

It is a cyclic number.

It is not a de Polignac number, because 6443981 - 2² = 6443977 is a prime.

It is a super-2 number, since 2×6443981² = 83049782256722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6443911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3221990 + 3221991.

It is an arithmetic number, because the mean of its divisors is an integer number (3221991).

Almost surely, 2^6443981 is an apocalyptic number.

It is an amenable number.

6443981 is a deficient number, since it is larger than the sum of its proper divisors (1).

6443981 is an equidigital number, since it uses as much as digits as its factorization.

6443981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 35.

The square root of 6443981 is about 2538.4997537916. The cubic root of 6443981 is about 186.0878780797.

The spelling of 6443981 in words is "six million, four hundred forty-three thousand, nine hundred eighty-one".