1161326561 has 4 divisors (see below), whose sum is σ = 1163389872. Its totient is φ = 1159263252.

The previous prime is 1161326539. The next prime is 1161326563. The reversal of 1161326561 is 1656231611.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1656231611 = 7393 ⋅224027.

It is a cyclic number.

It is not a de Polignac number, because 1161326561 - 2⁶ = 1161326497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1161326563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1030811 + ... + 1031936.

It is an arithmetic number, because the mean of its divisors is an integer number (290847468).

Almost surely, 2^1161326561 is an apocalyptic number.

It is an amenable number.

1161326561 is a deficient number, since it is larger than the sum of its proper divisors (2063311).

1161326561 is an equidigital number, since it uses as much as digits as its factorization.

1161326561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2063310.

The product of its digits is 6480, while the sum is 32.

The square root of 1161326561 is about 34078.2417533534. The cubic root of 1161326561 is about 1051.1179509260.

The spelling of 1161326561 in words is "one billion, one hundred sixty-one million, three hundred twenty-six thousand, five hundred sixty-one".