261643859 has 2 divisors, whose sum is σ = 261643860. Its totient is φ = 261643858.

The previous prime is 261643853. The next prime is 261643861. The reversal of 261643859 is 958346162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261643859 - 2¹⁶ = 261578323 is a prime.

Together with 261643861, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (261643853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130821929 + 130821930.

It is an arithmetic number, because the mean of its divisors is an integer number (130821930).

Almost surely, 2^261643859 is an apocalyptic number.

261643859 is a deficient number, since it is larger than the sum of its proper divisors (1).

261643859 is an equidigital number, since it uses as much as digits as its factorization.

261643859 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 44.

The square root of 261643859 is about 16175.4090829258. The cubic root of 261643859 is about 639.5927250909.

The spelling of 261643859 in words is "two hundred sixty-one million, six hundred forty-three thousand, eight hundred fifty-nine".