561761721 has 12 divisors (see below), whose sum is σ = 812366100. Its totient is φ = 374077440.

The previous prime is 561761687. The next prime is 561761741. The reversal of 561761721 is 127167165.

561761721 is a `hidden beast` number, since 5 + 6 + 17 + 617 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 281031696 + 280730025 = 16764^2 + 16755^2 .

It is not a de Polignac number, because 561761721 - 2¹⁰ = 561760697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (561761741) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27496 + ... + 43353.

It is an arithmetic number, because the mean of its divisors is an integer number (67697175).

Almost surely, 2^561761721 is an apocalyptic number.

It is an amenable number.

561761721 is a deficient number, since it is larger than the sum of its proper divisors (250604379).

561761721 is a wasteful number, since it uses less digits than its factorization.

561761721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71736 (or 71733 counting only the distinct ones).

The product of its digits is 17640, while the sum is 36.

The square root of 561761721 is about 23701.5130529677. The cubic root of 561761721 is about 825.1205069147.

The spelling of 561761721 in words is "five hundred sixty-one million, seven hundred sixty-one thousand, seven hundred twenty-one".