1821881281 has 4 divisors (see below), whose sum is σ = 1987506864. Its totient is φ = 1656255700.

The previous prime is 1821881273. The next prime is 1821881333.

1821881281 is nontrivially palindromic in base 10.

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 not a de Polignac number, because 1821881281 - 2³ = 1821881273 is a prime.

It is a super-3 number, since 3×1821881281³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1821881251) 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 3 ways as a sum of consecutive naturals, for example, 82812775 + ... + 82812796.

It is an arithmetic number, because the mean of its divisors is an integer number (496876716).

Almost surely, 2^1821881281 is an apocalyptic number.

1821881281 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1821881281 is a deficient number, since it is larger than the sum of its proper divisors (165625583).

1821881281 is a wasteful number, since it uses less digits than its factorization.

1821881281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165625582.

The product of its digits is 16384, while the sum is 40.

The square root of 1821881281 is about 42683.5012739114. The cubic root of 1821881281 is about 1221.3496845177.

It can be divided in two parts, 18218 and 81281, that added together give a palindrome (99499).

The spelling of 1821881281 in words is "one billion, eight hundred twenty-one million, eight hundred eighty-one thousand, two hundred eighty-one".