561691 has 4 divisors (see below), whose sum is σ = 604912. Its totient is φ = 518472.

The previous prime is 561667. The next prime is 561703. The reversal of 561691 is 196165.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196165 = 5 ⋅39233.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-561691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (561091) 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, 21591 + ... + 21616.

It is an arithmetic number, because the mean of its divisors is an integer number (151228).

2⁵⁶¹⁶⁹¹ is an apocalyptic number.

561691 is a deficient number, since it is larger than the sum of its proper divisors (43221).

561691 is a wasteful number, since it uses less digits than its factorization.

561691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43220.

The product of its digits is 1620, while the sum is 28.

The square root of 561691 is about 749.4604726068. The cubic root of 561691 is about 82.5085880255.

The spelling of 561691 in words is "five hundred sixty-one thousand, six hundred ninety-one".