261531811 has 2 divisors, whose sum is σ = 261531812. Its totient is φ = 261531810.

The previous prime is 261531797. The next prime is 261531817. The reversal of 261531811 is 118135162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261531811 - 2⁹ = 261531299 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261531811.

It is not a weakly prime, because it can be changed into another prime (261531817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130765905 + 130765906.

It is an arithmetic number, because the mean of its divisors is an integer number (130765906).

Almost surely, 2^261531811 is an apocalyptic number.

261531811 is a deficient number, since it is larger than the sum of its proper divisors (1).

261531811 is an equidigital number, since it uses as much as digits as its factorization.

261531811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 28.

The square root of 261531811 is about 16171.9451829395. The cubic root of 261531811 is about 639.5014109938.

Adding to 261531811 its reverse (118135162), we get a palindrome (379666973).

The spelling of 261531811 in words is "two hundred sixty-one million, five hundred thirty-one thousand, eight hundred eleven".