2809561 has 4 divisors (see below), whose sum is σ = 2900224. Its totient is φ = 2718900.

The previous prime is 2809559. The next prime is 2809567. The reversal of 2809561 is 1659082.

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.

It is a cyclic number.

It is not a de Polignac number, because 2809561 - 2¹ = 2809559 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 90631 = 2809561 / (2 + 8 + 0 + 9 + 5 + 6 + 1).

It is a Duffinian number.

2809561 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2809567) 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, 45285 + ... + 45346.

It is an arithmetic number, because the mean of its divisors is an integer number (725056).

2^2809561 is an apocalyptic number.

It is an amenable number.

2809561 is a deficient number, since it is larger than the sum of its proper divisors (90663).

2809561 is an equidigital number, since it uses as much as digits as its factorization.

2809561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90662.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 2809561 is about 1676.1745135874. The cubic root of 2809561 is about 141.1062191088.

The spelling of 2809561 in words is "two million, eight hundred nine thousand, five hundred sixty-one".