261611191 has 2 divisors, whose sum is σ = 261611192. Its totient is φ = 261611190.

The previous prime is 261611153. The next prime is 261611243. The reversal of 261611191 is 191116162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261611191 - 2¹⁵ = 261578423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261611101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130805595 + 130805596.

It is an arithmetic number, because the mean of its divisors is an integer number (130805596).

Almost surely, 2^261611191 is an apocalyptic number.

261611191 is a deficient number, since it is larger than the sum of its proper divisors (1).

261611191 is an equidigital number, since it uses as much as digits as its factorization.

261611191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 28.

The square root of 261611191 is about 16174.3992469581. The cubic root of 261611191 is about 639.5661048282.

The spelling of 261611191 in words is "two hundred sixty-one million, six hundred eleven thousand, one hundred ninety-one".