261817879 has 2 divisors, whose sum is σ = 261817880. Its totient is φ = 261817878.

The previous prime is 261817877. The next prime is 261817943. The reversal of 261817879 is 978718162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261817879 - 2¹ = 261817877 is a prime.

Together with 261817877, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261817877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130908939 + 130908940.

It is an arithmetic number, because the mean of its divisors is an integer number (130908940).

Almost surely, 2^261817879 is an apocalyptic number.

261817879 is a deficient number, since it is larger than the sum of its proper divisors (1).

261817879 is an equidigital number, since it uses as much as digits as its factorization.

261817879 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 338688, while the sum is 49.

The square root of 261817879 is about 16180.7873417828. The cubic root of 261817879 is about 639.7344919183.

The spelling of 261817879 in words is "two hundred sixty-one million, eight hundred seventeen thousand, eight hundred seventy-nine".