261501209 has 2 divisors, whose sum is σ = 261501210. Its totient is φ = 261501208.

The previous prime is 261501187. The next prime is 261501217. The reversal of 261501209 is 902105162.

261501209 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., 235776025 + 25725184 = 15355^2 + 5072^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261501209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (261501269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130750604 + 130750605.

It is an arithmetic number, because the mean of its divisors is an integer number (130750605).

Almost surely, 2^261501209 is an apocalyptic number.

It is an amenable number.

261501209 is a deficient number, since it is larger than the sum of its proper divisors (1).

261501209 is an equidigital number, since it uses as much as digits as its factorization.

261501209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 261501209 is about 16170.9990105745. Note that the first 3 decimals coincide. The cubic root of 261501209 is about 639.4764672015.

The spelling of 261501209 in words is "two hundred sixty-one million, five hundred one thousand, two hundred nine".