261335531 has 2 divisors, whose sum is σ = 261335532. Its totient is φ = 261335530.

The previous prime is 261335513. The next prime is 261335533. The reversal of 261335531 is 135533162.

Together with previous prime (261335513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261335531 - 2¹⁴ = 261319147 is a prime.

It is a super-2 number, since 2×261335531² = 136592519526103922, which contains 22 as substring.

Together with 261335533, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 261335494 and 261335503.

It is not a weakly prime, because it can be changed into another prime (261335533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130667765 + 130667766.

It is an arithmetic number, because the mean of its divisors is an integer number (130667766).

Almost surely, 2^261335531 is an apocalyptic number.

261335531 is a deficient number, since it is larger than the sum of its proper divisors (1).

261335531 is an equidigital number, since it uses as much as digits as its factorization.

261335531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8100, while the sum is 29.

The square root of 261335531 is about 16165.8755098510. The cubic root of 261335531 is about 639.3413887122.

Adding to 261335531 its reverse (135533162), we get a palindrome (396868693).

The spelling of 261335531 in words is "two hundred sixty-one million, three hundred thirty-five thousand, five hundred thirty-one".