Every Day Counts
Centred Square Prime Days
 
Age: 23,988 days
Date of birth
Your 40th Centred Square Prime Day is on
Tuesday
when you will be
24,421 days old

A centred square prime is a centred square number that is prime.

Unlike regular square numbers, which are never prime, quite a few of the centred square numbers are prime.

Centred square numbers are of the form n2 + (n - 1)2

In elementary number theory, a centred square number is a centred figurate number that gives the number of dots in a square with a dot in the centre and all other dots surrounding the centre dot in successive square layers. That is, each centred square number equals the number of dots within a given city block distance of the centre dot on a regular square lattice. While centred square numbers, like figurate numbers in general, have few if any direct practical applications, they are sometimes studied in recreational mathematics for their elegant geometric and arithmetic properties.

The figures for the first four centred square numbers are shown below:

Remind me, please


Next Prime Events
Day Age
Event
Days Ahead
Year Age
28 Oct 2019
23,993
5
65
11 Aug 2020
24,281
293
66
29 Dec 2020
24,421
433
66
28 May 2021
24,571
583
67
24 Feb 2025
25,939
1,951
71
04 Aug 2032
28,657
4,669
78
20 Jul 2036
30,103
6,115
82
24 Dec 2055
37,199
13,211
101
30 Nov 2061
39,367
15,379
107
01 Nov 2073
43,721
19,733
119
17 Dec 2075
44,497
20,509
121
31 Mar 2087
48,619
24,631
133
26 Jul 2133
65,537
41,549
179
08 Sep 2228
100,279
76,291
274
28 Mar 2252
108,881
84,893
298
29 Dec 2312
131,071
107,083
358
22 Apr 7771
2,124,679
2,100,691
5817
Ordinal
Day Age
Date
Age
1st
5
23 Feb 1954
0
2nd
13
03 Mar 1954
0
3rd
41
31 Mar 1954
0
4th
61
20 Apr 1954
0
5th
113
11 Jun 1954
0
6th
181
18 Aug 1954
0
7th
313
28 Dec 1954
0
8th
421
15 Apr 1955
1
9th
613
24 Oct 1955
1
10th
761
20 Mar 1956
2
11th
1,013
27 Nov 1956
2
12th
1,201
03 Jun 1957
3
13th
1,301
11 Sep 1957
3
14th
1,741
25 Nov 1958
4
15th
1,861
25 Mar 1959
5
16th
2,113
02 Dec 1959
5
17th
2,381
26 Aug 1960
6
18th
2,521
13 Jan 1961
6
19th
3,121
05 Sep 1962
8
20th
3,613
10 Jan 1964
9
21st
4,513
28 Jun 1966
12
22nd
5,101
06 Feb 1968
13
23rd
7,321
06 Mar 1974
20
24th
8,581
17 Aug 1977
23
25th
9,661
01 Aug 1980
26
26th
9,941
08 May 1981
27
27th
10,513
01 Dec 1982
28
28th
12,641
28 Sep 1988
34
29th
13,613
28 May 1991
37
30th
14,281
26 Mar 1993
39
31st
14,621
01 Mar 1994
40
32nd
15,313
22 Jan 1996
41
33rd
16,381
25 Dec 1998
44
34th
19,013
10 Mar 2006
52
35th
19,801
06 May 2008
54
36th
20,201
10 Jun 2009
55
37th
21,013
31 Aug 2011
57
38th
21,841
06 Dec 2013
59
39th
23,981
16 Oct 2019
65
40th
24,421
29 Dec 2020
66
1
41st
26,681
08 Mar 2027
73