261221065 has 32 divisors (see below), whose sum is σ = 387431424. Its totient is φ = 164981760.

The previous prime is 261221053. The next prime is 261221069. The reversal of 261221065 is 560122162.

It is not a de Polignac number, because 261221065 - 2⁵ = 261221033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261221069) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 23295 + ... + 32635.

It is an arithmetic number, because the mean of its divisors is an integer number (12107232).

Almost surely, 2^261221065 is an apocalyptic number.

It is an amenable number.

261221065 is a deficient number, since it is larger than the sum of its proper divisors (126210359).

261221065 is a wasteful number, since it uses less digits than its factorization.

261221065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9417.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 261221065 is about 16162.3347632698. The cubic root of 261221065 is about 639.2480303917.

The spelling of 261221065 in words is "two hundred sixty-one million, two hundred twenty-one thousand, sixty-five".