2561861 has 4 divisors (see below), whose sum is σ = 2610252. Its totient is φ = 2513472.

The previous prime is 2561857. The next prime is 2561863. The reversal of 2561861 is 1681652.

It is a happy number.

2561861 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2044900 + 516961 = 1430^2 + 719^2 .

It is not a de Polignac number, because 2561861 - 2² = 2561857 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24116 + ... + 24221.

It is an arithmetic number, because the mean of its divisors is an integer number (652563).

2^2561861 is an apocalyptic number.

It is an amenable number.

2561861 is a deficient number, since it is larger than the sum of its proper divisors (48391).

2561861 is an equidigital number, since it uses as much as digits as its factorization.

2561861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48390.

The product of its digits is 2880, while the sum is 29.

The square root of 2561861 is about 1600.5814568462. The cubic root of 2561861 is about 136.8312163011.

The spelling of 2561861 in words is "two million, five hundred sixty-one thousand, eight hundred sixty-one".