561981 has 12 divisors (see below), whose sum is σ = 871872. Its totient is φ = 321048.

The previous prime is 561973. The next prime is 561983. The reversal of 561981 is 189165.

It is a happy number.

561981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 561981 - 2³ = 561973 is a prime.

It is a super-2 number, since 2×561981² = 631645288722, which contains 22 as substring.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 561981.

It is not an unprimeable number, because it can be changed into a prime (561983) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1765 + ... + 2058.

It is an arithmetic number, because the mean of its divisors is an integer number (72656).

2⁵⁶¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

561981 is a deficient number, since it is larger than the sum of its proper divisors (309891).

561981 is a wasteful number, since it uses less digits than its factorization.

561981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3840 (or 3833 counting only the distinct ones).

The product of its digits is 2160, while the sum is 30.

The square root of 561981 is about 749.6539201525. The cubic root of 561981 is about 82.5227852584.

Subtracting from 561981 its reverse (189165), we obtain a triangular number (372816 = T₈₆₃).

The spelling of 561981 in words is "five hundred sixty-one thousand, nine hundred eighty-one".