261405817 has 2 divisors, whose sum is σ = 261405818. Its totient is φ = 261405816.

The previous prime is 261405799. The next prime is 261405853. The reversal of 261405817 is 718504162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 251571321 + 9834496 = 15861^2 + 3136^2 .

It is a cyclic number.

It is not a de Polignac number, because 261405817 - 2²³ = 253017209 is a prime.

It is a super-2 number, since 2×261405817² = 136666002322874978, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261405887) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130702908 + 130702909.

It is an arithmetic number, because the mean of its divisors is an integer number (130702909).

Almost surely, 2^261405817 is an apocalyptic number.

It is an amenable number.

261405817 is a deficient number, since it is larger than the sum of its proper divisors (1).

261405817 is an equidigital number, since it uses as much as digits as its factorization.

261405817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 261405817 is about 16168.0492639032. The cubic root of 261405817 is about 639.3987003742.

Adding to 261405817 its reverse (718504162), we get a palindrome (979909979).

The spelling of 261405817 in words is "two hundred sixty-one million, four hundred five thousand, eight hundred seventeen".