What dose the number mean in LSTM

Question

In RNN neural network,

what does the number 128 behind LSTM mean?

# RNN Recurrent Neural Network architecture 
model = Sequential()

model.add(LSTM(128, input_shape=(X_train.shape[1:]), return_sequences=True))
#model.add(Dropout(0.2))
model.add(BatchNormalization())

Answer 1

It is the number of LSTM node you want to use (perpendicular to the flow of information).