19921789 has 2 divisors, whose sum is σ = 19921790. Its totient is φ = 19921788.

The previous prime is 19921757. The next prime is 19921801. The reversal of 19921789 is 98712991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18748900 + 1172889 = 4330^2 + 1083^2 .

It is a cyclic number.

It is not a de Polignac number, because 19921789 - 2⁵ = 19921757 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19921589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9960894 + 9960895.

It is an arithmetic number, because the mean of its divisors is an integer number (9960895).

Almost surely, 2^19921789 is an apocalyptic number.

It is an amenable number.

19921789 is a deficient number, since it is larger than the sum of its proper divisors (1).

19921789 is an equidigital number, since it uses as much as digits as its factorization.

19921789 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 19921789 is about 4463.3831339019. The cubic root of 19921789 is about 271.0874705727.

The spelling of 19921789 in words is "nineteen million, nine hundred twenty-one thousand, seven hundred eighty-nine".