261251161 has 2 divisors, whose sum is σ = 261251162. Its totient is φ = 261251160.

The previous prime is 261251153. The next prime is 261251171. The reversal of 261251161 is 161152162.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 206209600 + 55041561 = 14360^2 + 7419^2 .

It is a cyclic number.

It is not a de Polignac number, because 261251161 - 2³ = 261251153 is a prime.

It is not a weakly prime, because it can be changed into another prime (261251131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130625580 + 130625581.

It is an arithmetic number, because the mean of its divisors is an integer number (130625581).

Almost surely, 2^261251161 is an apocalyptic number.

It is an amenable number.

261251161 is a deficient number, since it is larger than the sum of its proper divisors (1).

261251161 is an equidigital number, since it uses as much as digits as its factorization.

261251161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 25.

The square root of 261251161 is about 16163.2657900562. The cubic root of 261251161 is about 639.2725792923.

The spelling of 261251161 in words is "two hundred sixty-one million, two hundred fifty-one thousand, one hundred sixty-one".