261211217 has 2 divisors, whose sum is σ = 261211218. Its totient is φ = 261211216.

The previous prime is 261211199. The next prime is 261211271. The reversal of 261211217 is 712112162.

Together with next prime (261211271) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 164070481 + 97140736 = 12809^2 + 9856^2 .

It is a cyclic number.

It is not a de Polignac number, because 261211217 - 2¹⁴ = 261194833 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 261211192 and 261211201.

It is not a weakly prime, because it can be changed into another prime (261211117) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130605608 + 130605609.

It is an arithmetic number, because the mean of its divisors is an integer number (130605609).

Almost surely, 2^261211217 is an apocalyptic number.

It is an amenable number.

261211217 is a deficient number, since it is larger than the sum of its proper divisors (1).

261211217 is an equidigital number, since it uses as much as digits as its factorization.

261211217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 336, while the sum is 23.

The square root of 261211217 is about 16162.0301014446. The cubic root of 261211217 is about 639.2399971017.

Adding to 261211217 its reverse (712112162), we get a palindrome (973323379).

The spelling of 261211217 in words is "two hundred sixty-one million, two hundred eleven thousand, two hundred seventeen".