561331781 has 4 divisors (see below), whose sum is σ = 561948864. Its totient is φ = 560714700.

The previous prime is 561331753. The next prime is 561331783. The reversal of 561331781 is 187133165.

561331781 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, 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 561331781 - 2¹⁴ = 561315397 is a prime.

It is a super-2 number, since 2×561331781² = 630186736721263922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (561331783) 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, 307175 + ... + 308996.

It is an arithmetic number, because the mean of its divisors is an integer number (140487216).

Almost surely, 2^561331781 is an apocalyptic number.

It is an amenable number.

561331781 is a deficient number, since it is larger than the sum of its proper divisors (617083).

561331781 is an equidigital number, since it uses as much as digits as its factorization.

561331781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 617082.

The product of its digits is 15120, while the sum is 35.

The square root of 561331781 is about 23692.4414318153. The cubic root of 561331781 is about 824.9099533186.

The spelling of 561331781 in words is "five hundred sixty-one million, three hundred thirty-one thousand, seven hundred eighty-one".