2551561 has 4 divisors (see below), whose sum is σ = 2589712. Its totient is φ = 2513412.

The previous prime is 2551559. The next prime is 2551603. The reversal of 2551561 is 1651552.

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 2551561 - 2¹ = 2551559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2551501) 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, 18975 + ... + 19108.

It is an arithmetic number, because the mean of its divisors is an integer number (647428).

2^2551561 is an apocalyptic number.

It is an amenable number.

2551561 is a deficient number, since it is larger than the sum of its proper divisors (38151).

2551561 is an equidigital number, since it uses as much as digits as its factorization.

2551561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38150.

The product of its digits is 1500, while the sum is 25.

The square root of 2551561 is about 1597.3606355485. The cubic root of 2551561 is about 136.6475926847.

Subtracting from 2551561 its reverse (1651552), we obtain a palindrome (900009).

The spelling of 2551561 in words is "two million, five hundred fifty-one thousand, five hundred sixty-one".