1611611561 has 4 divisors (see below), whose sum is σ = 1841841792. Its totient is φ = 1381381332.

The previous prime is 1611611557. The next prime is 1611611621. The reversal of 1611611561 is 1651161161.

It is a happy number.

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 1611611561 - 2² = 1611611557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1611611531) 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, 115115105 + ... + 115115118.

It is an arithmetic number, because the mean of its divisors is an integer number (460460448).

Almost surely, 2^1611611561 is an apocalyptic number.

It is an amenable number.

1611611561 is a deficient number, since it is larger than the sum of its proper divisors (230230231).

1611611561 is an equidigital number, since it uses as much as digits as its factorization.

1611611561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230230230.

The product of its digits is 1080, while the sum is 29.

The square root of 1611611561 is about 40144.8821271155. The cubic root of 1611611561 is about 1172.4296458226.

The spelling of 1611611561 in words is "one billion, six hundred eleven million, six hundred eleven thousand, five hundred sixty-one".