17921989 has 2 divisors, whose sum is σ = 17921990. Its totient is φ = 17921988.

The previous prime is 17921987. The next prime is 17922001. The reversal of 17921989 is 98912971.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10857025 + 7064964 = 3295^2 + 2658^2 .

It is a cyclic number.

It is not a de Polignac number, because 17921989 - 2¹ = 17921987 is a prime.

It is a super-2 number, since 2×17921989² = 642395379432242, which contains 22 as substring.

Together with 17921987, 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 (17921987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8960994 + 8960995.

It is an arithmetic number, because the mean of its divisors is an integer number (8960995).

Almost surely, 2^17921989 is an apocalyptic number.

It is an amenable number.

17921989 is a deficient number, since it is larger than the sum of its proper divisors (1).

17921989 is an equidigital number, since it uses as much as digits as its factorization.

17921989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 81648, while the sum is 46.

The square root of 17921989 is about 4233.4370197276. The cubic root of 17921989 is about 261.6949862291.

The spelling of 17921989 in words is "seventeen million, nine hundred twenty-one thousand, nine hundred eighty-nine".