261813613 has 2 divisors, whose sum is σ = 261813614. Its totient is φ = 261813612.

The previous prime is 261813611. The next prime is 261813637. The reversal of 261813613 is 316318162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204690249 + 57123364 = 14307^2 + 7558^2 .

261813613 is a truncatable prime.

It is a cyclic number.

It is not a de Polignac number, because 261813613 - 2¹ = 261813611 is a prime.

It is a super-2 number, since 2×261813613² = 137092735904227538, which contains 22 as substring.

Together with 261813611, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261813611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130906806 + 130906807.

It is an arithmetic number, because the mean of its divisors is an integer number (130906807).

Almost surely, 2^261813613 is an apocalyptic number.

It is an amenable number.

261813613 is a deficient number, since it is larger than the sum of its proper divisors (1).

261813613 is an equidigital number, since it uses as much as digits as its factorization.

261813613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 31.

The square root of 261813613 is about 16180.6555182415. The cubic root of 261813613 is about 639.7310173374.

The spelling of 261813613 in words is "two hundred sixty-one million, eight hundred thirteen thousand, six hundred thirteen".