261861409 has 2 divisors, whose sum is σ = 261861410. Its totient is φ = 261861408.

The previous prime is 261861403. The next prime is 261861437. The reversal of 261861409 is 904168162.

It is a happy number.

261861409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 228856384 + 33005025 = 15128^2 + 5745^2 .

It is a cyclic number.

It is not a de Polignac number, because 261861409 - 2⁹ = 261860897 is a prime.

It is not a weakly prime, because it can be changed into another prime (261861403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130930704 + 130930705.

It is an arithmetic number, because the mean of its divisors is an integer number (130930705).

Almost surely, 2^261861409 is an apocalyptic number.

It is an amenable number.

261861409 is a deficient number, since it is larger than the sum of its proper divisors (1).

261861409 is an equidigital number, since it uses as much as digits as its factorization.

261861409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 261861409 is about 16182.1323996561. The cubic root of 261861409 is about 639.7699441690.

The spelling of 261861409 in words is "two hundred sixty-one million, eight hundred sixty-one thousand, four hundred nine".