1091555261 has 8 divisors (see below), whose sum is σ = 1159462584. Its totient is φ = 1024058880.

The previous prime is 1091555251. The next prime is 1091555279. The reversal of 1091555261 is 1625551901.

It can be written as a sum of positive squares in 4 ways, for example, as 244036 + 1091311225 = 494^2 + 33035^2 .

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 1091555261 - 2¹⁸ = 1091293117 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 (1091555251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 97250 + ... + 107891.

It is an arithmetic number, because the mean of its divisors is an integer number (144932823).

Almost surely, 2^1091555261 is an apocalyptic number.

It is an amenable number.

1091555261 is a deficient number, since it is larger than the sum of its proper divisors (67907323).

1091555261 is a wasteful number, since it uses less digits than its factorization.

1091555261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205471.

The product of its (nonzero) digits is 13500, while the sum is 35.

The square root of 1091555261 is about 33038.6933912345. The cubic root of 1091555261 is about 1029.6317095325.

The spelling of 1091555261 in words is "one billion, ninety-one million, five hundred fifty-five thousand, two hundred sixty-one".