261551 has 6 divisors (see below), whose sum is σ = 271752. Its totient is φ = 251720.

The previous prime is 261529. The next prime is 261557. The reversal of 261551 is 155162.

It is not a de Polignac number, because 261551 - 2¹⁰ = 260527 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 (261557) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 686 + ... + 996.

It is an arithmetic number, because the mean of its divisors is an integer number (45292).

2²⁶¹⁵⁵¹ is an apocalyptic number.

261551 is a deficient number, since it is larger than the sum of its proper divisors (10201).

261551 is an equidigital number, since it uses as much as digits as its factorization.

261551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369 (or 340 counting only the distinct ones).

The product of its digits is 300, while the sum is 20.

The square root of 261551 is about 511.4205705679. The cubic root of 261551 is about 63.9517051019.

The spelling of 261551 in words is "two hundred sixty-one thousand, five hundred fifty-one".