1643163860861 has 2 divisors, whose sum is σ = 1643163860862. Its totient is φ = 1643163860860.

The previous prime is 1643163860843. The next prime is 1643163860867. The reversal of 1643163860861 is 1680683613461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1624069872100 + 19093988761 = 1274390^2 + 138181^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643163860861 - 2¹⁴ = 1643163844477 is a prime.

It is a super-2 number, since 2×1643163860861² (a number of 25 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1643163860867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821581930430 + 821581930431.

It is an arithmetic number, because the mean of its divisors is an integer number (821581930431).

Almost surely, 2^{1643163860861} is an apocalyptic number.

It is an amenable number.

1643163860861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643163860861 is an equidigital number, since it uses as much as digits as its factorization.

1643163860861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2985984, while the sum is 53.

The spelling of 1643163860861 in words is "one trillion, six hundred forty-three billion, one hundred sixty-three million, eight hundred sixty thousand, eight hundred sixty-one".