factordbrpc · fdb
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Enter a value, an expression, or a term with a variable like 10^n+1 to list a range. Switch to Database id to look a number up by its stored id. Reading never stores anything; use Create to add a number to the database. See the expression syntax & functions reference.

P · Proven prime
below threshold 3 digits
★
Interesting number. 271441 = 521^2, the smallest Perrin pseudoprime, found by Adams and Shanks in 1982 - answering Perrin's 1899 question whether a composite n can divide the Perrin number P(n).

Value

521
521
‹ prev prime next prime ›
↪
Term #1 of the Home prime · Base 6 sequence of 40 · 2 terms
Term #1 of the Inverse home prime · Base 3 sequence of 346 · 2 terms
Term #1 of the Home prime · Base 12 sequence of 267 · 2 terms
Term #1 of the Home prime · Base 15 sequence of 142 · 2 terms
Term #1 of the Aliquot variants · Quasi · σ(n) − n − 1 sequence of 414 · 2 terms
Term #2 of the Inverse home prime · Base 12 sequence of 187 · 3 terms
Term #1 of the Inverse home prime · Base 14 sequence of 111 · 2 terms
Term #1 of the Inverse home prime · Base 30 sequence of 187 · 2 terms
Term #3 of the Conway climb · Base 6 sequence of 39 · 4 terms
Term #1 of the Conway climb · Base 12 sequence of 267 · 2 terms
Term #1 of the Conway climb · Base 15 sequence of 142 · 2 terms
Term #1 of the Prime-stopping maps · σ(n) − 1 until a prime sequence of 346 · 2 terms
Term #1 of the Distinct-prime home prime, descending · Base 3 sequence of 346 · 2 terms
Term #1 of the Mid-divisor concatenation · Base 8 sequence of 72 · 2 terms
Is factor of

Primality

Verified directlyproven prime

Checked deterministically (below 300 digits).

From the command linefdb · curl
fdb
fdb number '521' --detail 2
curl
curl -s 'https://factordb.com:4059/rpc' -H 'Content-Type: application/json' -d '{"jsonrpc":"2.0","id":1,"method":"get_number","params":{"target":{"expr":"521"},"decimal":false,"detail":2}}'