7 (number)

7 is the integer the proceeds 6 and precedes 8. 7 is both a Mersenne prime and a Woodall prime. A Mersenne prime is a prime number that is one less than a power of two. It is the only prime number preceding a cube.

To check if a number is divisible by 7, double the last digit of the number and subtract the result from the original number without the last digit, repeat this process if needed. If the final result is divisible by 7, then the original number is also divisible by 7. 7 is a Happy Number.  

In mathematics

7 < 6 | 8 >
0	1	2	3	4	5	6	7	8	9
10	11	12	13	14	15	16	17	18	19
20	21	22	23	24	25	26	27	28	29
30	31	32	33	34	35	36	37	38	39
40	41	42	43	44	45	46	47	48	49
50	51	52	53	54	55	56	57	58	59
60	61	62	63	64	65	66	67	68	69
70	71	72	73	74	75	76	77	78	79
80	81	82	83	84	85	86	87	88	89
90	91	92	93	94	95	96	97	98	99

Seven, recognized as the fourth prime number, is distinguished not only as a Mersenne prime (given that $2^{3}-1=7$) but also as a double Mersenne prime, as the exponent 3 is also a Mersenne prime.