261513209 has 2 divisors, whose sum is σ = 261513210. Its totient is φ = 261513208.

The previous prime is 261513199. The next prime is 261513233. The reversal of 261513209 is 902315162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 253701184 + 7812025 = 15928^2 + 2795^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261513209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (261513269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130756604 + 130756605.

It is an arithmetic number, because the mean of its divisors is an integer number (130756605).

Almost surely, 2^261513209 is an apocalyptic number.

It is an amenable number.

261513209 is a deficient number, since it is larger than the sum of its proper divisors (1).

261513209 is an equidigital number, since it uses as much as digits as its factorization.

261513209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 261513209 is about 16171.3700409087. The cubic root of 261513209 is about 639.4862486735.

The spelling of 261513209 in words is "two hundred sixty-one million, five hundred thirteen thousand, two hundred nine".