261856621 has 8 divisors (see below), whose sum is σ = 285863480. Its totient is φ = 238401792.

The previous prime is 261856619. The next prime is 261856649. The reversal of 261856621 is 126658162.

It can be written as a sum of positive squares in 4 ways, for example, as 9523396 + 252333225 = 3086^2 + 15885^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261856621 - 2¹ = 261856619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261856681) 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 7 ways as a sum of consecutive naturals, for example, 137016 + ... + 138913.

It is an arithmetic number, because the mean of its divisors is an integer number (35732935).

Almost surely, 2^261856621 is an apocalyptic number.

It is an amenable number.

261856621 is a deficient number, since it is larger than the sum of its proper divisors (24006859).

261856621 is a wasteful number, since it uses less digits than its factorization.

261856621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276015.

The product of its digits is 34560, while the sum is 37.

The square root of 261856621 is about 16181.9844580323. The cubic root of 261856621 is about 639.7660448581.

The spelling of 261856621 in words is "two hundred sixty-one million, eight hundred fifty-six thousand, six hundred twenty-one".