I'm trying to call a stored procedure using ADO .NET and I'm getting the following error:

ORA-01460 - unimplemented or unreasonable conversion requested

The stored procedure I'm trying to call has the following parameters:

param1 IN VARCHAR2,
param2 IN NUMBER,
param3 IN VARCHAR2,
param4 OUT NUMBER,
param5 OUT NUMBER,
param6 OUT NUMBER,
param7 OUT VARCHAR2

Below is the C# code I'm using to call the stored procedure:

    OracleCommand command = connection.CreateCommand();
    command.CommandType = CommandType.StoredProcedure;
    command.CommandText = "MY_PROC";

    OracleParameter param1 = new OracleParameter() { ParameterName = "param1", Direction = ParameterDirection.Input,
        Value = p1, OracleDbType = OracleDbType.Varchar2, Size = p1.Length };
    OracleParameter param2 = new OracleParameter() { ParameterName = "param2", Direction = ParameterDirection.Input,
        Value = p2, OracleDbType = OracleDbType.Decimal };
    OracleParameter param3 = new OracleParameter() { ParameterName = "param3", Direction = ParameterDirection.Input,
        Value = p3, OracleDbType = OracleDbType.Varchar2, Size = p3.Length };

    OracleParameter param4 = new OracleParameter() { ParameterName = "param4", Direction = ParameterDirection.Output,
        OracleDbType = OracleDbType.Decimal };
    OracleParameter param5 = new OracleParameter() { ParameterName = "param5", Direction = ParameterDirection.Output,
        OracleDbType = OracleDbType.Decimal};
    OracleParameter param6 = new OracleParameter() { ParameterName = "param6", Direction = ParameterDirection.Output,
        OracleDbType = OracleDbType.Decimal };
    OracleParameter param7 = new OracleParameter() { ParameterName = "param7", Direction = ParameterDirection.Output,
        OracleDbType = OracleDbType.Varchar2, Size = 32767 };

    command.Parameters.Add(param1);
    command.Parameters.Add(param2);
    command.Parameters.Add(param3);
    command.Parameters.Add(param4);
    command.Parameters.Add(param5);
    command.Parameters.Add(param6);
    command.Parameters.Add(param7);

    command.ExecuteNonQuery();

Any ideas what I'm doing wrong?