An irrational number cannot be expressed as a fraction of two integers. Let's analyze the options:
- \(-1529\) is an integer, which is a rational number.
- \(0.343434...\) is a repeating decimal, which can be expressed as a fraction (it is rational).
- \(2\sqrt{3}\): Since \(\sqrt{3}\) is an irrational number, multiplying it by 2 makes \(2\sqrt{3}\) also irrational.
- \(87.9821\) is a decimal that terminates, which means it can be expressed as a fraction and is thus rational.
Based on this analysis, the irrational number among the options given is \(2\sqrt{3}\).