1985771856989 has 2 divisors, whose sum is σ = 1985771856990. Its totient is φ = 1985771856988.

The previous prime is 1985771856983. The next prime is 1985771857019. The reversal of 1985771856989 is 9896581775891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1766108102500 + 219663754489 = 1328950^2 + 468683^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1985771856989 is a prime.

It is a super-2 number, since 2×1985771856989² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1985771856983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 992885928494 + 992885928495.

It is an arithmetic number, because the mean of its divisors is an integer number (992885928495).

Almost surely, 2^{1985771856989} is an apocalyptic number.

It is an amenable number.

1985771856989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1985771856989 is an equidigital number, since it uses as much as digits as its factorization.

1985771856989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2743372800, while the sum is 83.

The spelling of 1985771856989 in words is "one trillion, nine hundred eighty-five billion, seven hundred seventy-one million, eight hundred fifty-six thousand, nine hundred eighty-nine".