561521287681 has 4 divisors (see below), whose sum is σ = 572116029012. Its totient is φ = 550926546352.

The previous prime is 561521287673. The next prime is 561521287709. The reversal of 561521287681 is 186782125165.

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 140631750081 + 420889537600 = 375009^2 + 648760^2 .

It is a cyclic number.

It is not a de Polignac number, because 561521287681 - 2³ = 561521287673 is a prime.

It is a super-2 number, since 2×561521287681² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (561521287631) 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, 5297370586 + ... + 5297370691.

It is an arithmetic number, because the mean of its divisors is an integer number (143029007253).

Almost surely, 2^561521287681 is an apocalyptic number.

It is an amenable number.

561521287681 is a deficient number, since it is larger than the sum of its proper divisors (10594741331).

561521287681 is a wasteful number, since it uses less digits than its factorization.

561521287681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10594741330.

The product of its digits is 1612800, while the sum is 52.

The spelling of 561521287681 in words is "five hundred sixty-one billion, five hundred twenty-one million, two hundred eighty-seven thousand, six hundred eighty-one".