261643321 has 2 divisors, whose sum is σ = 261643322. Its totient is φ = 261643320.

The previous prime is 261643309. The next prime is 261643363. The reversal of 261643321 is 123346162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 222755625 + 38887696 = 14925^2 + 6236^2 .

It is a cyclic number.

It is not a de Polignac number, because 261643321 - 2¹⁵ = 261610553 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261643321.

It is not a weakly prime, because it can be changed into another prime (261643301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130821660 + 130821661.

It is an arithmetic number, because the mean of its divisors is an integer number (130821661).

Almost surely, 2^261643321 is an apocalyptic number.

It is an amenable number.

261643321 is a deficient number, since it is larger than the sum of its proper divisors (1).

261643321 is an equidigital number, since it uses as much as digits as its factorization.

261643321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 28.

The square root of 261643321 is about 16175.3924527351. The cubic root of 261643321 is about 639.5922867073.

Adding to 261643321 its reverse (123346162), we get a palindrome (384989483).

The spelling of 261643321 in words is "two hundred sixty-one million, six hundred forty-three thousand, three hundred twenty-one".