561208661 has 4 divisors (see below), whose sum is σ = 604378572. Its totient is φ = 518038752.

The previous prime is 561208657. The next prime is 561208663. The reversal of 561208661 is 166802165.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 314530225 + 246678436 = 17735^2 + 15706^2 .

It is a cyclic number.

It is not a de Polignac number, because 561208661 - 2² = 561208657 is a prime.

It is a super-2 number, since 2×561208661² = 629910322362825842, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (561208663) 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, 21584936 + ... + 21584961.

It is an arithmetic number, because the mean of its divisors is an integer number (151094643).

Almost surely, 2^561208661 is an apocalyptic number.

It is an amenable number.

561208661 is a deficient number, since it is larger than the sum of its proper divisors (43169911).

561208661 is a wasteful number, since it uses less digits than its factorization.

561208661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43169910.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 561208661 is about 23689.8429923037. The cubic root of 561208661 is about 824.8496382232.

The spelling of 561208661 in words is "five hundred sixty-one million, two hundred eight thousand, six hundred sixty-one".