261546781 has 2 divisors, whose sum is σ = 261546782. Its totient is φ = 261546780.

The previous prime is 261546713. The next prime is 261546797. The reversal of 261546781 is 187645162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 229522500 + 32024281 = 15150^2 + 5659^2 .

It is a cyclic number.

It is not a de Polignac number, because 261546781 - 2⁷ = 261546653 is a prime.

It is a super-2 number, since 2×261546781² = 136813437302923922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261546281) 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, 130773390 + 130773391.

It is an arithmetic number, because the mean of its divisors is an integer number (130773391).

Almost surely, 2^261546781 is an apocalyptic number.

It is an amenable number.

261546781 is a deficient number, since it is larger than the sum of its proper divisors (1).

261546781 is an equidigital number, since it uses as much as digits as its factorization.

261546781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80640, while the sum is 40.

The square root of 261546781 is about 16172.4080148876. The cubic root of 261546781 is about 639.5136123821.

The spelling of 261546781 in words is "two hundred sixty-one million, five hundred forty-six thousand, seven hundred eighty-one".