10001561681 has 2 divisors, whose sum is σ = 10001561682. Its totient is φ = 10001561680.

The previous prime is 10001561629. The next prime is 10001561693. The reversal of 10001561681 is 18616510001.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9816846400 + 184715281 = 99080^2 + 13591^2 .

It is an emirp because it is prime and its reverse (18616510001) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 10001561681 - 2⁶ = 10001561617 is a prime.

It is a super-2 number, since 2×10001561681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (10001561611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5000780840 + 5000780841.

It is an arithmetic number, because the mean of its divisors is an integer number (5000780841).

Almost surely, 2^10001561681 is an apocalyptic number.

It is an amenable number.

10001561681 is a deficient number, since it is larger than the sum of its proper divisors (1).

10001561681 is an equidigital number, since it uses as much as digits as its factorization.

10001561681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 29.

The spelling of 10001561681 in words is "ten billion, one million, five hundred sixty-one thousand, six hundred eighty-one".