2781561 has 4 divisors (see below), whose sum is σ = 3708752. Its totient is φ = 1854372.

The previous prime is 2781521. The next prime is 2781577. The reversal of 2781561 is 1651872.

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 not a de Polignac number, because 2781561 - 2⁶ = 2781497 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2781521) 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, 463591 + ... + 463596.

It is an arithmetic number, because the mean of its divisors is an integer number (927188).

2^2781561 is an apocalyptic number.

It is an amenable number.

2781561 is a deficient number, since it is larger than the sum of its proper divisors (927191).

2781561 is an equidigital number, since it uses as much as digits as its factorization.

2781561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 927190.

The product of its digits is 3360, while the sum is 30.

The square root of 2781561 is about 1667.8012471515. The cubic root of 2781561 is about 140.6358997971.

The spelling of 2781561 in words is "two million, seven hundred eighty-one thousand, five hundred sixty-one".