/** ******************************
 * Singapore mobile phone number *
 *********************************/
/**
 * starts with 8, 9
 * reference: https://en.wikipedia.org/wiki/Telephone_numbers_in_Singapore
 */
export declare function is_sg_mobile_phone_prefix(tel: string): boolean;
/**
 * with/without +65 prefix
 */
export declare function is_sg_mobile_phone(tel: number | string): boolean;
/**
 * very forgiving
 *
 * @returns +65xxxxyyyy if valid
 *          empty string if not valid
 */
export declare function to_full_sg_mobile_phone(tel: string | number): string;
/**
 * @returns +65 xxxx yyyy if valid
 */
export declare function format_sg_mobile_phone(tel: string | number): string;