261155287 has 4 divisors (see below), whose sum is σ = 268213576. Its totient is φ = 254097000.

The previous prime is 261155263. The next prime is 261155303. The reversal of 261155287 is 782551162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 782551162 = 2 ⋅391275581.

It is a cyclic number.

It is not a de Polignac number, because 261155287 - 2¹¹ = 261153239 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 7058251 = 261155287 / (2 + 6 + 1 + 1 + 5 + 5 + 2 + 8 + 7).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261155227) 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 3 ways as a sum of consecutive naturals, for example, 3529089 + ... + 3529162.

It is an arithmetic number, because the mean of its divisors is an integer number (67053394).

Almost surely, 2^261155287 is an apocalyptic number.

261155287 is a deficient number, since it is larger than the sum of its proper divisors (7058289).

261155287 is an equidigital number, since it uses as much as digits as its factorization.

261155287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7058288.

The product of its digits is 33600, while the sum is 37.

The square root of 261155287 is about 16160.2997187552. The cubic root of 261155287 is about 639.1943696008.

The spelling of 261155287 in words is "two hundred sixty-one million, one hundred fifty-five thousand, two hundred eighty-seven".