1099561 has 4 divisors (see below), whose sum is σ = 1147392. Its totient is φ = 1051732.

The previous prime is 1099559. The next prime is 1099573. The reversal of 1099561 is 1659901.

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: 1659901 = 131 ⋅12671.

It is a cyclic number.

It is not a de Polignac number, because 1099561 - 2¹ = 1099559 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

1099561 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1099541) 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, 23881 + ... + 23926.

It is an arithmetic number, because the mean of its divisors is an integer number (286848).

2^1099561 is an apocalyptic number.

1099561 is the 561-st centered heptagonal number.

It is an amenable number.

1099561 is a deficient number, since it is larger than the sum of its proper divisors (47831).

1099561 is an equidigital number, since it uses as much as digits as its factorization.

1099561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47830.

The product of its (nonzero) digits is 2430, while the sum is 31.

The square root of 1099561 is about 1048.5995422467. The cubic root of 1099561 is about 103.2142772647.

The spelling of 1099561 in words is "one million, ninety-nine thousand, five hundred sixty-one".