Help with syntax error - Mailing list pgsql-general

I have these tables:

CREATE TABLE IF NOT EXISTS registrar (
index SERIAL,
registrar_id TEXT,
day TEXT NOT NULL,
month TEXT NOT NULL,
year TEXT NOT NULL,
hour TEXT NOT NULL,
minute TEXT NOT NULL,
second TEXT NOT NULL,
millisecond TEXT NOT NULL,
am_pm TEXT NOT NULL,
admin BOOLEAN NOT NULL DEFAULT false,
CONSTRAINT key PRIMARY KEY (registrar_id) );

CREATE TABLE IF NOT EXISTS user_name (
user_name_id TEXT PRIMARY KEY REFERENCES registrar(registrar_id),
first_name TEXT NOT NULL,
middle_name TEXT NOT NULL,
last_name TEXT NOT NULL);

When I enter the following pg commands :

INSERT INTO registrar VALUES (DEFAULT, '18551420601012L23', '1', '12', '2024', '18', '55', '14', '207', 'PM');
INSERT INTO user_name '18551420601012L23', 'John', 'Fitzgerald', 'Kennedy'); <= UserNameTable.write()

I get this message :

Exception in thread "main" java.sql.SQLException: In company.contact.Company$UserNameTable.write()
ERROR: syntax error at or near "'18551420601012L23'"
  Position: 23

The error is in the user_name_id, which is a primary that references the table "registrar" 's "registrar_id" primary key.
According to the documentation, the insertion should be OK, no?

What am I doing wrong?