261815123 has 2 divisors, whose sum is σ = 261815124. Its totient is φ = 261815122.

The previous prime is 261815107. The next prime is 261815143. The reversal of 261815123 is 321518162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261815123 - 2⁴ = 261815107 is a prime.

It is not a weakly prime, because it can be changed into another prime (261815143) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130907561 + 130907562.

It is an arithmetic number, because the mean of its divisors is an integer number (130907562).

Almost surely, 2^261815123 is an apocalyptic number.

261815123 is a deficient number, since it is larger than the sum of its proper divisors (1).

261815123 is an equidigital number, since it uses as much as digits as its factorization.

261815123 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 29.

The square root of 261815123 is about 16180.7021788302. The cubic root of 261815123 is about 639.7322472098.

The spelling of 261815123 in words is "two hundred sixty-one million, eight hundred fifteen thousand, one hundred twenty-three".