261335521 has 4 divisors (see below), whose sum is σ = 261563332. Its totient is φ = 261107712.

The previous prime is 261335513. The next prime is 261335531. The reversal of 261335521 is 125533162.

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 244484496 + 16851025 = 15636^2 + 4105^2 .

It is a cyclic number.

It is not a de Polignac number, because 261335521 - 2³ = 261335513 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261335521.

It is not an unprimeable number, because it can be changed into a prime (261335531) 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, 112176 + ... + 114481.

It is an arithmetic number, because the mean of its divisors is an integer number (65390833).

Almost surely, 2^261335521 is an apocalyptic number.

It is an amenable number.

261335521 is a deficient number, since it is larger than the sum of its proper divisors (227811).

261335521 is a wasteful number, since it uses less digits than its factorization.

261335521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227810.

The product of its digits is 5400, while the sum is 28.

The square root of 261335521 is about 16165.8752005575. The cubic root of 261335521 is about 639.3413805574.

Adding to 261335521 its reverse (125533162), we get a palindrome (386868683).

The spelling of 261335521 in words is "two hundred sixty-one million, three hundred thirty-five thousand, five hundred twenty-one".