1561001016181 has 2 divisors, whose sum is σ = 1561001016182. Its totient is φ = 1561001016180.

The previous prime is 1561001016139. The next prime is 1561001016187. The reversal of 1561001016181 is 1816101001651.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 842971878225 + 718029137956 = 918135^2 + 847366^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561001016181 - 2¹⁹ = 1561000491893 is a prime.

It is a super-2 number, since 2×1561001016181² (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 (1561001016187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780500508090 + 780500508091.

It is an arithmetic number, because the mean of its divisors is an integer number (780500508091).

Almost surely, 2^{1561001016181} is an apocalyptic number.

It is an amenable number.

1561001016181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561001016181 is an equidigital number, since it uses as much as digits as its factorization.

1561001016181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 31.

The spelling of 1561001016181 in words is "one trillion, five hundred sixty-one billion, one million, sixteen thousand, one hundred eighty-one".