561781 has 4 divisors (see below), whose sum is σ = 612864. Its totient is φ = 510700.

The previous prime is 561767. The next prime is 561787. The reversal of 561781 is 187165.

It is a happy number.

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 561781 - 2¹³ = 553589 is a prime.

It is a super-2 number, since 2×561781² = 631195783922, 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 (561787) 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, 25525 + ... + 25546.

It is an arithmetic number, because the mean of its divisors is an integer number (153216).

2⁵⁶¹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

561781 is a deficient number, since it is larger than the sum of its proper divisors (51083).

561781 is a wasteful number, since it uses less digits than its factorization.

561781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51082.

The product of its digits is 1680, while the sum is 28.

The square root of 561781 is about 749.5205133951. The cubic root of 561781 is about 82.5129945861.

The spelling of 561781 in words is "five hundred sixty-one thousand, seven hundred eighty-one".