261998857 has 2 divisors, whose sum is σ = 261998858. Its totient is φ = 261998856.

The previous prime is 261998827. The next prime is 261998861. The reversal of 261998857 is 758899162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 137921536 + 124077321 = 11744^2 + 11139^2 .

It is a cyclic number.

It is not a de Polignac number, because 261998857 - 2⁷ = 261998729 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 261998798 and 261998807.

It is not a weakly prime, because it can be changed into another prime (261998827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130999428 + 130999429.

It is an arithmetic number, because the mean of its divisors is an integer number (130999429).

Almost surely, 2^261998857 is an apocalyptic number.

It is an amenable number.

261998857 is a deficient number, since it is larger than the sum of its proper divisors (1).

261998857 is an equidigital number, since it uses as much as digits as its factorization.

261998857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2177280, while the sum is 55.

The square root of 261998857 is about 16186.3787488122. The cubic root of 261998857 is about 639.8818605178.

The spelling of 261998857 in words is "two hundred sixty-one million, nine hundred ninety-eight thousand, eight hundred fifty-seven".