261561611 has 2 divisors, whose sum is σ = 261561612. Its totient is φ = 261561610.

The previous prime is 261561571. The next prime is 261561617. The reversal of 261561611 is 116165162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261561611 - 2¹⁴ = 261545227 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (261561617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130780805 + 130780806.

It is an arithmetic number, because the mean of its divisors is an integer number (130780806).

Almost surely, 2^261561611 is an apocalyptic number.

261561611 is a deficient number, since it is larger than the sum of its proper divisors (1).

261561611 is an equidigital number, since it uses as much as digits as its factorization.

261561611 is an evil number, because the sum of its binary digits is even.

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

The square root of 261561611 is about 16172.8665053540. The cubic root of 261561611 is about 639.5256992034.

The spelling of 261561611 in words is "two hundred sixty-one million, five hundred sixty-one thousand, six hundred eleven".