261835681 has 2 divisors, whose sum is σ = 261835682. Its totient is φ = 261835680.

The previous prime is 261835631. The next prime is 261835709. The reversal of 261835681 is 186538162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 153363456 + 108472225 = 12384^2 + 10415^2 .

It is a cyclic number.

It is not a de Polignac number, because 261835681 - 2⁹ = 261835169 is a prime.

It is a super-2 number, since 2×261835681² = 137115847689467522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261835621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130917840 + 130917841.

It is an arithmetic number, because the mean of its divisors is an integer number (130917841).

Almost surely, 2^261835681 is an apocalyptic number.

It is an amenable number.

261835681 is a deficient number, since it is larger than the sum of its proper divisors (1).

261835681 is an equidigital number, since it uses as much as digits as its factorization.

261835681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69120, while the sum is 40.

The square root of 261835681 is about 16181.3374292733. The cubic root of 261835681 is about 639.7489909222.

The spelling of 261835681 in words is "two hundred sixty-one million, eight hundred thirty-five thousand, six hundred eighty-one".