561551721 has 8 divisors (see below), whose sum is σ = 756454944. Its totient is φ = 370508160.

The previous prime is 561551719. The next prime is 561551741. The reversal of 561551721 is 127155165.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 561551721 - 2¹ = 561551719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (561551741) 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, 964575 + ... + 965156.

It is an arithmetic number, because the mean of its divisors is an integer number (94556868).

Almost surely, 2^561551721 is an apocalyptic number.

It is an amenable number.

561551721 is a deficient number, since it is larger than the sum of its proper divisors (194903223).

561551721 is a wasteful number, since it uses less digits than its factorization.

561551721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1929831.

The product of its digits is 10500, while the sum is 33.

The square root of 561551721 is about 23697.0825419502. The cubic root of 561551721 is about 825.0176774908.

The spelling of 561551721 in words is "five hundred sixty-one million, five hundred fifty-one thousand, seven hundred twenty-one".