261811409 has 2 divisors, whose sum is σ = 261811410. Its totient is φ = 261811408.

The previous prime is 261811397. The next prime is 261811421. The reversal of 261811409 is 904118162.

It is a balanced prime because it is at equal distance from previous prime (261811397) and next prime (261811421).

It can be written as a sum of positive squares in only one way, i.e., 251920384 + 9891025 = 15872^2 + 3145^2 .

It is a cyclic number.

It is not a de Polignac number, because 261811409 - 2¹⁶ = 261745873 is a prime.

It is not a weakly prime, because it can be changed into another prime (261811489) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130905704 + 130905705.

It is an arithmetic number, because the mean of its divisors is an integer number (130905705).

Almost surely, 2^261811409 is an apocalyptic number.

It is an amenable number.

261811409 is a deficient number, since it is larger than the sum of its proper divisors (1).

261811409 is an equidigital number, since it uses as much as digits as its factorization.

261811409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 261811409 is about 16180.5874120812. The cubic root of 261811409 is about 639.7292222040.

The spelling of 261811409 in words is "two hundred sixty-one million, eight hundred eleven thousand, four hundred nine".