64843981 has 2 divisors, whose sum is σ = 64843982. Its totient is φ = 64843980.

The previous prime is 64843949. The next prime is 64843993. The reversal of 64843981 is 18934846.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 34703881 + 30140100 = 5891^2 + 5490^2 .

It is a cyclic number.

It is not a de Polignac number, because 64843981 - 2⁵ = 64843949 is a prime.

It is a super-2 number, since 2×64843981² = 8409483743856722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64843901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32421990 + 32421991.

It is an arithmetic number, because the mean of its divisors is an integer number (32421991).

Almost surely, 2^64843981 is an apocalyptic number.

It is an amenable number.

64843981 is a deficient number, since it is larger than the sum of its proper divisors (1).

64843981 is an equidigital number, since it uses as much as digits as its factorization.

64843981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 43.

The square root of 64843981 is about 8052.5760474521. The cubic root of 64843981 is about 401.7506208890.

The spelling of 64843981 in words is "sixty-four million, eight hundred forty-three thousand, nine hundred eighty-one".