2001561491 has 2 divisors, whose sum is σ = 2001561492. Its totient is φ = 2001561490.

The previous prime is 2001561467. The next prime is 2001561503. The reversal of 2001561491 is 1941651002.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 2001561491 - 2⁶ = 2001561427 is a prime.

It is not a weakly prime, because it can be changed into another prime (2001561421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000780745 + 1000780746.

It is an arithmetic number, because the mean of its divisors is an integer number (1000780746).

Almost surely, 2^2001561491 is an apocalyptic number.

2001561491 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001561491 is an equidigital number, since it uses as much as digits as its factorization.

2001561491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 2001561491 is about 44738.8141438729. The cubic root of 2001561491 is about 1260.2488571617.

The spelling of 2001561491 in words is "two billion, one million, five hundred sixty-one thousand, four hundred ninety-one".