1981451922161 has 4 divisors (see below), whose sum is σ = 2035004676852. Its totient is φ = 1927899167472.

The previous prime is 1981451922143. The next prime is 1981451922167. The reversal of 1981451922161 is 1612291541891.

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 1522521549025 + 458930373136 = 1233905^2 + 677444^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981451922161 is a prime.

It is a super-3 number, since 3×1981451922161³ (a number of 38 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981451922167) 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, 26776377290 + ... + 26776377363.

It is an arithmetic number, because the mean of its divisors is an integer number (508751169213).

Almost surely, 2^{1981451922161} is an apocalyptic number.

It is an amenable number.

1981451922161 is a deficient number, since it is larger than the sum of its proper divisors (53552754691).

1981451922161 is an equidigital number, since it uses as much as digits as its factorization.

1981451922161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53552754690.

The product of its digits is 311040, while the sum is 50.

The spelling of 1981451922161 in words is "one trillion, nine hundred eighty-one billion, four hundred fifty-one million, nine hundred twenty-two thousand, one hundred sixty-one".