261513509 has 2 divisors, whose sum is σ = 261513510. Its totient is φ = 261513508.

The previous prime is 261513491. The next prime is 261513517. The reversal of 261513509 is 905315162.

261513509 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 137124100 + 124389409 = 11710^2 + 11153^2 .

It is a cyclic number.

It is not a de Polignac number, because 261513509 - 2²⁴ = 244736293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261513559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130756754 + 130756755.

It is an arithmetic number, because the mean of its divisors is an integer number (130756755).

Almost surely, 2^261513509 is an apocalyptic number.

It is an amenable number.

261513509 is a deficient number, since it is larger than the sum of its proper divisors (1).

261513509 is an equidigital number, since it uses as much as digits as its factorization.

261513509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8100, while the sum is 32.

The square root of 261513509 is about 16171.3793165580. The cubic root of 261513509 is about 639.4864932065.

The spelling of 261513509 in words is "two hundred sixty-one million, five hundred thirteen thousand, five hundred nine".