1801981999 has 2 divisors, whose sum is σ = 1801982000. Its totient is φ = 1801981998.

The previous prime is 1801981969. The next prime is 1801982009. The reversal of 1801981999 is 9991891081.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1801981999 - 2⁷ = 1801981871 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1801981949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 900990999 + 900991000.

It is an arithmetic number, because the mean of its divisors is an integer number (900991000).

Almost surely, 2^1801981999 is an apocalyptic number.

1801981999 is a deficient number, since it is larger than the sum of its proper divisors (1).

1801981999 is an equidigital number, since it uses as much as digits as its factorization.

1801981999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 419904, while the sum is 55.

The square root of 1801981999 is about 42449.7585269928. The cubic root of 1801981999 is about 1216.8867137954.

The spelling of 1801981999 in words is "one billion, eight hundred one million, nine hundred eighty-one thousand, nine hundred ninety-nine".