1643993240081 has 2 divisors, whose sum is σ = 1643993240082. Its totient is φ = 1643993240080.

The previous prime is 1643993239997. The next prime is 1643993240167. The reversal of 1643993240081 is 1800423993461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1111582227856 + 532411012225 = 1054316^2 + 729665^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1643993240081 is a prime.

It is a super-2 number, since 2×1643993240081² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1643993248081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821996620040 + 821996620041.

It is an arithmetic number, because the mean of its divisors is an integer number (821996620041).

Almost surely, 2^{1643993240081} is an apocalyptic number.

It is an amenable number.

1643993240081 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643993240081 is an equidigital number, since it uses as much as digits as its factorization.

1643993240081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1119744, while the sum is 50.

The spelling of 1643993240081 in words is "one trillion, six hundred forty-three billion, nine hundred ninety-three million, two hundred forty thousand, eighty-one".