3561781 has 4 divisors (see below), whose sum is σ = 3567564. Its totient is φ = 3556000.

The previous prime is 3561773. The next prime is 3561799. The reversal of 3561781 is 1871653.

3561781 = 1334² + 1335².

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 1779556 + 1782225 = 1334^2 + 1335^2 .

It is a cyclic number.

It is not a de Polignac number, because 3561781 - 2³ = 3561773 is a prime.

It is a super-2 number, since 2×3561781² = 25372567783922, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3561581) 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, 1840 + ... + 3241.

It is an arithmetic number, because the mean of its divisors is an integer number (891891).

Almost surely, 2^3561781 is an apocalyptic number.

3561781 is the 1335-th centered square number.

It is an amenable number.

3561781 is a deficient number, since it is larger than the sum of its proper divisors (5783).

3561781 is an equidigital number, since it uses as much as digits as its factorization.

3561781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5782.

The product of its digits is 5040, while the sum is 31.

The square root of 3561781 is about 1887.2681314535. The cubic root of 3561781 is about 152.7175931709.

It can be divided in two parts, 35 and 61781, that added together give a palindrome (61816).

The spelling of 3561781 in words is "three million, five hundred sixty-one thousand, seven hundred eighty-one".