561500721 has 8 divisors (see below), whose sum is σ = 831852960. Its totient is φ = 374333796.

The previous prime is 561500717. The next prime is 561500759. The reversal of 561500721 is 127005165.

561500721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 561500721 - 2² = 561500717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 20796323 = 561500721 / (5 + 6 + 1 + 5 + 0 + 0 + 7 + 2 + 1).

It is not an unprimeable number, because it can be changed into a prime (561500761) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10398135 + ... + 10398188.

It is an arithmetic number, because the mean of its divisors is an integer number (103981620).

Almost surely, 2^561500721 is an apocalyptic number.

It is an amenable number.

561500721 is a deficient number, since it is larger than the sum of its proper divisors (270352239).

561500721 is a wasteful number, since it uses less digits than its factorization.

561500721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20796332 (or 20796326 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 27.

The square root of 561500721 is about 23696.0064356845. The cubic root of 561500721 is about 824.9927007619.

Adding to 561500721 its reverse (127005165), we get a palindrome (688505886).

The spelling of 561500721 in words is "five hundred sixty-one million, five hundred thousand, seven hundred twenty-one".