1105721561 has 4 divisors (see below), whose sum is σ = 1263681792. Its totient is φ = 947761332.

The previous prime is 1105721543. The next prime is 1105721597. The reversal of 1105721561 is 1651275011.

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: 1651275011 = 1237 ⋅1334903.

It is not a de Polignac number, because 1105721561 - 2¹⁰ = 1105720537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1105721521) 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, 78980105 + ... + 78980118.

It is an arithmetic number, because the mean of its divisors is an integer number (315920448).

Almost surely, 2^1105721561 is an apocalyptic number.

It is an amenable number.

1105721561 is a deficient number, since it is larger than the sum of its proper divisors (157960231).

1105721561 is an equidigital number, since it uses as much as digits as its factorization.

1105721561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157960230.

The product of its (nonzero) digits is 2100, while the sum is 29.

The square root of 1105721561 is about 33252.3918087105. The cubic root of 1105721561 is about 1034.0667951044.

Adding to 1105721561 its reverse (1651275011), we get a palindrome (2756996572).

The spelling of 1105721561 in words is "one billion, one hundred five million, seven hundred twenty-one thousand, five hundred sixty-one".