2128991881 has 3 divisors (see below), whose sum is σ = 2129038023. Its totient is φ = 2128945740.

The previous prime is 2128991833. The next prime is 2128991911. The reversal of 2128991881 is 1881998212.

It is a happy number.

The square root of 2128991881 is 46141.

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.

It can be written as a sum of positive squares in only one way, i.e., 152300281 + 1976691600 = 12341^2 + 44460^2 .

It is not a de Polignac number, because 2128991881 - 2¹¹ = 2128989833 is a prime.

It is a super-2 number, since 2×2128991881² = 9065212858727836322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2128991801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 23071 + ... + 69211.

It is an arithmetic number, because the mean of its divisors is an integer number (709679341).

Almost surely, 2^2128991881 is an apocalyptic number.

2128991881 is the 46141-st square number.

2128991881 is the 23071-st centered octagonal number.

It is an amenable number.

2128991881 is a deficient number, since it is larger than the sum of its proper divisors (46142).

2128991881 is an frugal number, since it uses more digits than its factorization.

2128991881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92282 (or 46141 counting only the distinct ones).

The product of its digits is 165888, while the sum is 49.

The cubic root of 2128991881 is about 1286.4453309828.

Multiplying 2128991881 by its sum of digits (49), we get a square (104320602169 = 322987²).

It can be divided in two parts, 2128 and 991881, that added together give a square (994009 = 997²).

The spelling of 2128991881 in words is "two billion, one hundred twenty-eight million, nine hundred ninety-one thousand, eight hundred eighty-one".