Could you, in a few seconds, mentally multiply two arbitrarily chosen multi-digit numbers, divide two prime numbers and give the answer, say, to 20 decimals, or raise any 2-or 3-digit number to the fifth power (e.g., 675 × 486 = ?, 31:61 = ?, 985 = ?)? If yes, then you may be one of the very few people known as “calculating prodigies,” “lightning calculators,” or simply “expert calculators,” who possess exceptional calculating abilities. Calculating prodigies are individuals able to mentally solve complex calculations that most people would be unable to solve without much time and effort. Such prodigies can add, multiply, subtract, or divide multidigit numbers, raise to powers, extract roots, calculate sines, and much more. They can be found among great mathematicians and scientists but also among individuals, some with developmental delay, intellectual, neurological, or neuropsychiatric disorders, who exhibit outstanding focal calculating abilities without exceptional mathematical talent. Calculating prodigies have always been a source of puzzlement for their contemporaries. On the one hand, famous scientists and mathematicians impress because their expertise is usually thought to stem from some rare, high level of intellectual efficiency. On the other hand, mnemonists and calculators with developmental delay raise the question of whether or not they really possess exceptional capacities or are simply playing some ingenious tricks.