On 2025 and Other Torn Numbers.

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Bibliographic Details
Title: On 2025 and Other Torn Numbers.
Authors: Javaheri, Mohammad (AUTHOR) mjavaheri@siena.edu
Source: American Mathematical Monthly. May2026, Vol. 133 Issue 5, p478-484. 7p.
Subject Terms: Prime factors (Mathematics), Number theory
Abstract: 2025 is an example of a torn number, a perfect square that is a fixed point of the following split-add-square procedure: the number is torn in half (as 20 and 25), then the two parts are added together ( 20 + 25 = 45 ), and finally the result is squared ( 45 2 = 2025 ). We show that there exist at least 2 μ (k) − 1 2k-digit torn numbers, k ≥ 1 , where μ (k) is the number of prime factors of 10 k − 1 . Moreover, we show that the split-add-square procedure has infinitely many periodic points of any arbitrary period. [ABSTRACT FROM AUTHOR]
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Database: Education Research Complete
Description
Abstract:2025 is an example of a torn number, a perfect square that is a fixed point of the following split-add-square procedure: the number is torn in half (as 20 and 25), then the two parts are added together ( 20 + 25 = 45 ), and finally the result is squared ( 45 2 = 2025 ). We show that there exist at least 2 μ (k) − 1 2k-digit torn numbers, k ≥ 1 , where μ (k) is the number of prime factors of 10 k − 1 . Moreover, we show that the split-add-square procedure has infinitely many periodic points of any arbitrary period. [ABSTRACT FROM AUTHOR]
ISSN:00029890
DOI:10.1080/00029890.2025.2561491