261291 has 8 divisors (see below), whose sum is σ = 350784. Its totient is φ = 173000.

The previous prime is 261281. The next prime is 261301. The reversal of 261291 is 192162.

It is an interprime number because it is at equal distance from previous prime (261281) and next prime (261301).

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 261291 - 2¹⁵ = 228523 is a prime.

It is an Ulam number.

261291 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (261241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 580 + ... + 926.

It is an arithmetic number, because the mean of its divisors is an integer number (43848).

2²⁶¹²⁹¹ is an apocalyptic number.

261291 is a deficient number, since it is larger than the sum of its proper divisors (89493).

261291 is a wasteful number, since it uses less digits than its factorization.

261291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 601.

The product of its digits is 216, while the sum is 21.

The square root of 261291 is about 511.1663134441. The cubic root of 261291 is about 63.9305072527.

The spelling of 261291 in words is "two hundred sixty-one thousand, two hundred ninety-one".