261686545 has 4 divisors (see below), whose sum is σ = 314023860. Its totient is φ = 209349232.

The previous prime is 261686527. The next prime is 261686549. The reversal of 261686545 is 545686162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 80299521 + 181387024 = 8961^2 + 13468^2 .

It is a cyclic number.

It is not a de Polignac number, because 261686545 - 2¹¹ = 261684497 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261686549) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26168650 + ... + 26168659.

It is an arithmetic number, because the mean of its divisors is an integer number (78505965).

Almost surely, 2^261686545 is an apocalyptic number.

It is an amenable number.

261686545 is a deficient number, since it is larger than the sum of its proper divisors (52337315).

261686545 is an equidigital number, since it uses as much as digits as its factorization.

261686545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52337314.

The product of its digits is 345600, while the sum is 43.

The square root of 261686545 is about 16176.7285011525. The cubic root of 261686545 is about 639.6275054097.

The spelling of 261686545 in words is "two hundred sixty-one million, six hundred eighty-six thousand, five hundred forty-five".