11720561 has 4 divisors (see below), whose sum is σ = 11790912. Its totient is φ = 11650212.

The previous prime is 11720551. The next prime is 11720567. The reversal of 11720561 is 16502711.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 11720561 - 2¹⁸ = 11458417 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (11720567) 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, 34925 + ... + 35258.

It is an arithmetic number, because the mean of its divisors is an integer number (2947728).

Almost surely, 2^11720561 is an apocalyptic number.

It is an amenable number.

11720561 is a deficient number, since it is larger than the sum of its proper divisors (70351).

11720561 is an equidigital number, since it uses as much as digits as its factorization.

11720561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70350.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 11720561 is about 3423.5304876691. The cubic root of 11720561 is about 227.1517741427.

It can be divided in two parts, 11 and 720561, that multiplied together give a triangular number (7926171 = T₃₉₈₁).

The spelling of 11720561 in words is "eleven million, seven hundred twenty thousand, five hundred sixty-one".