The document discusses four different methods for Bangla handwritten digit recognition. Method 1 uses preprocessing techniques like binarization, noise reduction, and segmentation followed by feature extraction and classification with a CNN. It achieves 94% accuracy. Method 2 also uses a CNN called MathNET with data augmentation, achieving 97% accuracy. Method 3 uses preprocessing, HOG feature extraction, and an SVM classifier, achieving 97.08% accuracy. Method 4 develops a dataset, performs data augmentation, uses a multi-layer CNN model with ensembling, and achieves 96.788% accuracy even on noisy images. The methods demonstrate high and improving recognition accuracy for Bangla handwritten digits.