.CustOTPBox {
    width: 30px;
    height: 40px;
    color: #fff;
    background-color: darkgray;
    border: 1px solid darkgray;
    font-size:18px;
}
 
input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
-webkit-appearance: none;
-moz-appearance: none;
appearance: none;
margin: 0;