18000491989 has 2 divisors, whose sum is σ = 18000491990. Its totient is φ = 18000491988.

The previous prime is 18000491987. The next prime is 18000492011. The reversal of 18000491989 is 98919400081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15319012900 + 2681479089 = 123770^2 + 51783^2 .

It is a cyclic number.

It is not a de Polignac number, because 18000491989 - 2¹ = 18000491987 is a prime.

It is a super-2 number, since 2×18000491989² (a number of 21 digits) contains 22 as substring.

Together with 18000491987, 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 (18000491987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9000245994 + 9000245995.

It is an arithmetic number, because the mean of its divisors is an integer number (9000245995).

Almost surely, 2^18000491989 is an apocalyptic number.

It is an amenable number.

18000491989 is a deficient number, since it is larger than the sum of its proper divisors (1).

18000491989 is an equidigital number, since it uses as much as digits as its factorization.

18000491989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 186624, while the sum is 49.

The spelling of 18000491989 in words is "eighteen billion, four hundred ninety-one thousand, nine hundred eighty-nine".