1191561361 has 3 divisors (see below), whose sum is σ = 1191595881. Its totient is φ = 1191526842.

The previous prime is 1191561359. The next prime is 1191561379. The reversal of 1191561361 is 1631651911.

It is a happy number.

The square root of 1191561361 is 34519.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1631651911 = 29 ⋅56263859.

It is not a de Polignac number, because 1191561361 - 2¹ = 1191561359 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1191561961) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 17260 + ... + 51778.

It is an arithmetic number, because the mean of its divisors is an integer number (397198627).

Almost surely, 2^1191561361 is an apocalyptic number.

1191561361 is the 34519-th square number.

1191561361 is the 17260-th centered octagonal number.

It is an amenable number.

1191561361 is a deficient number, since it is larger than the sum of its proper divisors (34520).

1191561361 is an frugal number, since it uses more digits than its factorization.

1191561361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69038 (or 34519 counting only the distinct ones).

The product of its digits is 4860, while the sum is 34.

The cubic root of 1191561361 is about 1060.1617650948.

The spelling of 1191561361 in words is "one billion, one hundred ninety-one million, five hundred sixty-one thousand, three hundred sixty-one".