105561721 has 4 divisors (see below), whose sum is σ = 111771252. Its totient is φ = 99352192.

The previous prime is 105561719. The next prime is 105561749. The reversal of 105561721 is 127165501.

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 92852496 + 12709225 = 9636^2 + 3565^2 .

It is a cyclic number.

It is not a de Polignac number, because 105561721 - 2¹ = 105561719 is a prime.

It is a super-2 number, since 2×105561721² = 22286553880963682, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 105561721.

It is not an unprimeable number, because it can be changed into a prime (105561751) 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, 3104740 + ... + 3104773.

It is an arithmetic number, because the mean of its divisors is an integer number (27942813).

Almost surely, 2^105561721 is an apocalyptic number.

It is an amenable number.

105561721 is a deficient number, since it is larger than the sum of its proper divisors (6209531).

105561721 is an equidigital number, since it uses as much as digits as its factorization.

105561721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6209530.

The product of its (nonzero) digits is 2100, while the sum is 28.

The square root of 105561721 is about 10274.3233840482. The cubic root of 105561721 is about 472.6091809321.

The spelling of 105561721 in words is "one hundred five million, five hundred sixty-one thousand, seven hundred twenty-one".