Number of the day: 9871

Properties of the number 9871:

9871 is a cyclic number.
9871 is the 1218^th prime.
9871 has 5 antidivisors and 9870 totatives.
9871 has a semiprime digit sum 25 in base 10.
Reversing the decimal digits of 9871 results in an emirp.
9871 = 4936² - 4935² is the difference of 2 nonnegative squares in 1 way.
9871 is the sum of 2 positive triangular numbers.
9871 is the difference of 2 positive pentagonal numbers in 1 way.
9871 is not the sum of 3 positive squares.
9871² is the sum of 3 positive squares.
9871 is a proper divisor of 419³⁵ - 1.
9871 = '9' + '871' is the concatenation of 2 semiprime numbers.
9871 = '987' + '1' is the concatenation of 2 Fibonacci numbers.
9871 is an emirp in (at least) the following bases: 5, 10, 11, 17, 18, 20, 35, 41, 42, 43, 44, 45, 52, 53, 55, 56, 59, 61, 65, 69, 74, 76, 77, 87, 88, and 93.
9871 is palindromic in (at least) the following bases: 29, 36, 94, and -71.
9871 in base 3 = 111112121 and consists of only the digits '1' and '2'.
9871 in base 21 = 1181 and consists of only the digits '1' and '8'.
9871 in base 29 = blb and consists of only the digits 'b' and 'l'.
9871 in base 36 = 7m7 and consists of only the digits '7' and 'm'.
9871 in base 37 = 77T and consists of only the digits '7' and 'T'.
9871 in base 40 = 66V and consists of only the digits '6' and 'V'.

The number 9871 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A007810: Largest prime with n distinct decimal digits.
A030540: Largest n-digit norep emirp.
A053072: Primes p such that p-12, p and p+12 are consecutive primes.
A055469: Primes of the form k(k+1)/2+1 (i.e., central polygonal numbers, or one more than triangular numbers).
A071361: Largest n-digit prime with strictly decreasing digits.
A073102: Primes of the form 210n + 1.
A120160: a(n)=ceiling( sum_{i=1..n-1} a(i)/4), a(1)=1.
A188135: a(n) = 8*n^2 + 2*n + 1.
A188382: Primes of the form 8*n^2 + 2*n + 1.
A267503: Primes n such that n-1 is squarefree and all prime divisors of n-1 other than 5 are in the sequence.