261541621 has 12 divisors (see below), whose sum is σ = 290339532. Its totient is φ = 235400000.

The previous prime is 261541607. The next prime is 261541627. The reversal of 261541621 is 126145162.

It can be written as a sum of positive squares in 2 ways, for example, as 166771396 + 94770225 = 12914^2 + 9735^2 .

It is not a de Polignac number, because 261541621 - 2⁹ = 261541109 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 261541621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261541627) 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 in 11 ways as a sum of consecutive naturals, for example, 1521 + ... + 22921.

It is an arithmetic number, because the mean of its divisors is an integer number (24194961).

Almost surely, 2^261541621 is an apocalyptic number.

It is an amenable number.

261541621 is a deficient number, since it is larger than the sum of its proper divisors (28797911).

261541621 is a wasteful number, since it uses less digits than its factorization.

261541621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21524 (or 21513 counting only the distinct ones).

The product of its digits is 2880, while the sum is 28.

The square root of 261541621 is about 16172.2484831269. The cubic root of 261541621 is about 639.5094067457.

Adding to 261541621 its reverse (126145162), we get a palindrome (387686783).

The spelling of 261541621 in words is "two hundred sixty-one million, five hundred forty-one thousand, six hundred twenty-one".