.back_to_top{
    padding: 3px;
    width: 45px;
    height: 45px ;
    border-radius: 50%;
    position: fixed;
    bottom: 50px;
    right: 50px;
    overflow: hidden;
    text-align: center;
    cursor: pointer;
    background-color:  #183484;
    border: 5px solid #00a5ff;
    display: block;
    z-index: 10;
}
.back_to_top:hover{
    cursor: pointer;
}
.back_to_top span{
    color: #fff;
    font-size: 26px;
    position: absolute;
    top: -2px;
    right: 6px;
}