Every Day Counts
Centred Square Prime Days
 
Age: 20,326 days
Date of birth
Your 37th Centred Square Prime Day is on
Friday
when you will be
21,013 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
21 Sep 2018
20,327
tomorrow
55
21 Oct 2018
20,357
31
55
23 Oct 2018
20,359
33
55
07 Aug 2020
21,013
687
57
26 Jun 2022
21,701
1,375
59
11 Jul 2024
22,447
2,121
61
12 Jul 2041
28,657
8,331
78
27 Jun 2045
30,103
9,777
82
30 Nov 2064
37,199
16,873
101
07 Nov 2070
39,367
19,041
107
09 Oct 2082
43,721
23,395
119
07 Mar 2096
48,619
28,293
133
03 Jul 2142
65,537
45,211
179
16 Aug 2237
100,279
79,953
274
05 Mar 2261
108,881
88,555
298
06 Dec 2321
131,071
110,745
358
29 Mar 7780
2,124,679
2,104,353
5817
Ordinal
Day Age
Date
Age
1st
5
31 Jan 1963
0
2nd
13
08 Feb 1963
0
3rd
41
08 Mar 1963
0
4th
61
28 Mar 1963
0
5th
113
19 May 1963
0
6th
181
26 Jul 1963
0
7th
313
05 Dec 1963
0
8th
421
22 Mar 1964
1
9th
613
30 Sep 1964
1
10th
761
25 Feb 1965
2
11th
1,013
04 Nov 1965
2
12th
1,201
11 May 1966
3
13th
1,301
19 Aug 1966
3
14th
1,741
02 Nov 1967
4
15th
1,861
01 Mar 1968
5
16th
2,113
08 Nov 1968
5
17th
2,381
03 Aug 1969
6
18th
2,521
21 Dec 1969
6
19th
3,121
13 Aug 1971
8
20th
3,613
17 Dec 1972
9
21st
4,513
05 Jun 1975
12
22nd
5,101
13 Jan 1977
13
23rd
7,321
11 Feb 1983
20
24th
8,581
25 Jul 1986
23
25th
9,661
09 Jul 1989
26
26th
9,941
15 Apr 1990
27
27th
10,513
08 Nov 1991
28
28th
12,641
05 Sep 1997
34
29th
13,613
04 May 2000
37
30th
14,281
03 Mar 2002
39
31st
14,621
06 Feb 2003
40
32nd
15,313
29 Dec 2004
41
33rd
16,381
02 Dec 2007
44
34th
19,013
15 Feb 2015
52
35th
19,801
13 Apr 2017
54
36th
20,201
18 May 2018
55
37th
21,013
07 Aug 2020
57
1
38th
21,841
13 Nov 2022
59
39th
23,981
22 Sep 2028
65
40th
24,421
06 Dec 2029
66
41st
26,681
13 Feb 2036
73