A number divisible by 99 is a natural number divisible by 9 and 1 1 at the same time. Its characteristic is to separate two digits from the right of this number, and then the sum can be divisible by 99, so this number can be divisible by 99. The method used here is "two-bit truncation method".

Elementary school 1 to grade 6 mathematics knowledge summary;

The first grade of primary school: 99 multiplication formula, learn basic addition and subtraction multiplication formula: recite 99 multiplication formula well and be familiar with single-digit multiplication formula;

The second grade of primary school: improve the multiplication formula table, strengthen the knowledge of the first grade, and learn the mixed operation of division and basic geometry;

The third grade of primary school: learn multiplication and commutation law, geometric area perimeter, time and unit. Distance calculation, distribution law, fractional decimal;

The fourth grade of primary school: the natural number of line angle is an integer, the prime factor is trapezoidal symmetry, and the fraction is calculated;

The fifth grade of primary school: multiplication and division of fractions and decimals, algebraic equations and average values, comparative size transformation, graphic area and volume;

Sixth grade: proportional percentage probability, circular fan, cylinder and cone.