561540 has 72 divisors (see below), whose sum is σ = 1838592. Its totient is φ = 127680.

The previous prime is 561529. The next prime is 561551. The reversal of 561540 is 45165.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (561529) and next prime (561551).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

561540 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2845 + ... + 3035.

It is an arithmetic number, because the mean of its divisors is an integer number (25536).

2⁵⁶¹⁵⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 561540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (919296).

561540 is an abundant number, since it is smaller than the sum of its proper divisors (1277052).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

561540 is a wasteful number, since it uses less digits than its factorization.

561540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 208 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 561540 is about 749.3597267001. The cubic root of 561540 is about 82.5011937385.

It can be divided in two parts, 56 and 1540, that added together give a triangular number (1596 = T₅₆).

The spelling of 561540 in words is "five hundred sixty-one thousand, five hundred forty".