1821880981 has 2 divisors, whose sum is σ = 1821880982. Its totient is φ = 1821880980.

The previous prime is 1821880979. The next prime is 1821880993. The reversal of 1821880981 is 1890881281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1817657956 + 4223025 = 42634^2 + 2055^2 .

It is an emirp because it is prime and its reverse (1890881281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1821880981 - 2¹ = 1821880979 is a prime.

It is a super-2 number, since 2×1821880981² = 6638500617859044722, which contains 22 as substring.

Together with 1821880979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1821880381) 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 as a sum of consecutive naturals, namely, 910940490 + 910940491.

It is an arithmetic number, because the mean of its divisors is an integer number (910940491).

Almost surely, 2^1821880981 is an apocalyptic number.

It is an amenable number.

1821880981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1821880981 is an equidigital number, since it uses as much as digits as its factorization.

1821880981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 73728, while the sum is 46.

The square root of 1821880981 is about 42683.4977596729. The cubic root of 1821880981 is about 1221.3496174799.

It can be divided in two parts, 18218 and 80981, that added together give a palindrome (99199).

The spelling of 1821880981 in words is "one billion, eight hundred twenty-one million, eight hundred eighty thousand, nine hundred eighty-one".