999121789 has 2 divisors, whose sum is σ = 999121790. Its totient is φ = 999121788.

The previous prime is 999121787. The next prime is 999121793. The reversal of 999121789 is 987121999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 525188889 + 473932900 = 22917^2 + 21770^2 .

It is a cyclic number.

It is not a de Polignac number, because 999121789 - 2¹ = 999121787 is a prime.

Together with 999121787, 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 (999121787) 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, 499560894 + 499560895.

It is an arithmetic number, because the mean of its divisors is an integer number (499560895).

Almost surely, 2^999121789 is an apocalyptic number.

It is an amenable number.

999121789 is a deficient number, since it is larger than the sum of its proper divisors (1).

999121789 is an equidigital number, since it uses as much as digits as its factorization.

999121789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 734832, while the sum is 55.

The square root of 999121789 is about 31608.8878165620. The cubic root of 999121789 is about 999.7071772632.

The spelling of 999121789 in words is "nine hundred ninety-nine million, one hundred twenty-one thousand, seven hundred eighty-nine".