1812116561 has 4 divisors (see below), whose sum is σ = 1814106624. Its totient is φ = 1810126500.

The previous prime is 1812116519. The next prime is 1812116573. The reversal of 1812116561 is 1656112181.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1656112181 = 19 ⋅87163799.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1812116561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1812116261) 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, 993665 + ... + 995486.

It is an arithmetic number, because the mean of its divisors is an integer number (453526656).

Almost surely, 2^1812116561 is an apocalyptic number.

It is an amenable number.

1812116561 is a deficient number, since it is larger than the sum of its proper divisors (1990063).

1812116561 is an equidigital number, since it uses as much as digits as its factorization.

1812116561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1990062.

The product of its digits is 2880, while the sum is 32.

The square root of 1812116561 is about 42568.9624139466. The cubic root of 1812116561 is about 1219.1637557400.

The spelling of 1812116561 in words is "one billion, eight hundred twelve million, one hundred sixteen thousand, five hundred sixty-one".