1001187556861 has 2 divisors, whose sum is σ = 1001187556862. Its totient is φ = 1001187556860.

The previous prime is 1001187556711. The next prime is 1001187556867. The reversal of 1001187556861 is 1686557811001.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 570614052100 + 430573504761 = 755390^2 + 656181^2 .

It is a cyclic number.

It is not a de Polignac number, because 1001187556861 - 2¹⁵ = 1001187524093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1001187556867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 500593778430 + 500593778431.

It is an arithmetic number, because the mean of its divisors is an integer number (500593778431).

Almost surely, 2^{1001187556861} is an apocalyptic number.

It is an amenable number.

1001187556861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1001187556861 is an equidigital number, since it uses as much as digits as its factorization.

1001187556861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 403200, while the sum is 49.

The spelling of 1001187556861 in words is "one trillion, one billion, one hundred eighty-seven million, five hundred fifty-six thousand, eight hundred sixty-one".