261288591 has 8 divisors (see below), whose sum is σ = 353291904. Its totient is φ = 171738840.

The previous prime is 261288583. The next prime is 261288607. The reversal of 261288591 is 195882162.

It is a happy number.

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

It is not a de Polignac number, because 261288591 - 2³ = 261288583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261288541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 613141 + ... + 613566.

It is an arithmetic number, because the mean of its divisors is an integer number (44161488).

Almost surely, 2^261288591 is an apocalyptic number.

261288591 is a deficient number, since it is larger than the sum of its proper divisors (92003313).

261288591 is a wasteful number, since it uses less digits than its factorization.

261288591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1226781.

The product of its digits is 69120, while the sum is 42.

The square root of 261288591 is about 16164.4236210265. The cubic root of 261288591 is about 639.3031078074.

The spelling of 261288591 in words is "two hundred sixty-one million, two hundred eighty-eight thousand, five hundred ninety-one".