561566261 has 4 divisors (see below), whose sum is σ = 591122400. Its totient is φ = 532010124.

The previous prime is 561566251. The next prime is 561566263. The reversal of 561566261 is 162665165.

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 a de Polignac number, because none of the positive numbers 2^k-561566261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (561566263) 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, 14778041 + ... + 14778078.

It is an arithmetic number, because the mean of its divisors is an integer number (147780600).

Almost surely, 2^561566261 is an apocalyptic number.

It is an amenable number.

561566261 is a deficient number, since it is larger than the sum of its proper divisors (29556139).

561566261 is a wasteful number, since it uses less digits than its factorization.

561566261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29556138.

The product of its digits is 64800, while the sum is 38.

The square root of 561566261 is about 23697.3893287847. The cubic root of 561566261 is about 825.0247980302.

The spelling of 561566261 in words is "five hundred sixty-one million, five hundred sixty-six thousand, two hundred sixty-one".