111777217561 has 3 divisors (see below), whose sum is σ = 111777551893. Its totient is φ = 111776883230.

The previous prime is 111777217547. The next prime is 111777217579. The reversal of 111777217561 is 165712777111.

The square root of 111777217561 is 334331.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 165712777111 = 7 ⋅23673253873.

It is not a de Polignac number, because 111777217561 - 2¹¹ = 111777215513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (111777217501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 167166 + ... + 501496.

Almost surely, 2^111777217561 is an apocalyptic number.

111777217561 is the 334331-st square number.

111777217561 is the 167166-th centered octagonal number.

It is an amenable number.

111777217561 is a deficient number, since it is larger than the sum of its proper divisors (334332).

111777217561 is an frugal number, since it uses more digits than its factorization.

111777217561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668662 (or 334331 counting only the distinct ones).

The product of its digits is 144060, while the sum is 46.

The spelling of 111777217561 in words is "one hundred eleven billion, seven hundred seventy-seven million, two hundred seventeen thousand, five hundred sixty-one".