561721 has 4 divisors (see below), whose sum is σ = 566272. Its totient is φ = 557172.

The previous prime is 561713. The next prime is 561733. The reversal of 561721 is 127165.

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 561721 - 2³ = 561713 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 561692 and 561701.

It is not an unprimeable number, because it can be changed into a prime (561761) 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, 2085 + ... + 2338.

It is an arithmetic number, because the mean of its divisors is an integer number (141568).

2⁵⁶¹⁷²¹ is an apocalyptic number.

It is an amenable number.

561721 is a deficient number, since it is larger than the sum of its proper divisors (4551).

561721 is a wasteful number, since it uses less digits than its factorization.

561721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4550.

The product of its digits is 420, while the sum is 22.

The square root of 561721 is about 749.4804867373. The cubic root of 561721 is about 82.5100569313.

Adding to 561721 its reverse (127165), we get a palindrome (688886).

The spelling of 561721 in words is "five hundred sixty-one thousand, seven hundred twenty-one".