Number of the day: 2621

Properties of the number 2621:

2621 is the 381^th prime.
2621 has 7 antidivisors and 2620 totatives.
2621 has a prime digit sum 11 in base 10.
Reversing the decimal digits of 2621 results in a semiprime.
2621 = 1311² - 1310² is the difference of 2 nonnegative squares in 1 way.
2621 is the sum of 2 positive triangular numbers.
2621 is the difference of 2 positive pentagonal numbers in 1 way.
2621 = 11² + 50² is the sum of 2 positive squares in 1 way.
2621 = 11² + 14² + 48² is the sum of 3 positive squares.
2621² = 1100² + 2379² is the sum of 2 positive squares in 1 way.
2621² is the sum of 3 positive squares.
2621 is a divisor of 761¹⁰ - 1.
2621 = '26' + '21' is the concatenation of 2 semiprime numbers.
2621 is an emirp in (at least) the following bases: 3, 5, 7, 11, 12, 13, 19, 21, 25, 26, 29, 31, 37, 41, 42, 43, 45, 47, 51, 53, 55, 58, 60, 69, 70, 71, 81, 84, 88, 90, 93, 94, 95, and 99.
2621 is palindromic in (at least) the following bases: 15, -10, -24, and -34.
2621 in base 15 = b9b and consists of only the digits '9' and 'b'.
2621 in base 25 = 44l and consists of only the digits '4' and 'l'.
2621 in base 29 = 33b and consists of only the digits '3' and 'b'.

The number 2621 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A007641: Primes of form 2n^2+29.
A096700: Balanced primes of order eight.
A099970: Write 1/e as a binary fraction; read this from left to right and whenever a 1 appears, note the integer formed by reading leftwards from that 1. Then divide these numbers by 2.
A107132: Primes of the form 2x^2+13y^2.
A117876: Primes p=prime(k) of level (1,2), i.e. such that A118534(k) = prime(k-2).
A124575: Triangle read by rows: row n is the first row of the matrix M[n]^(n-1), where M[n] is the n X n tridiagonal matrix with main diagonal (2,4,4,...) and super- and subdiagonals (1,1,1,...).
A141881: Primes congruent to 1 mod 20.
A164288: Members of A164368 which are not Ramanujan primes.
A164294: Primes prime(k) such that all integers in [(prime(k-1)+1)/2,(prime(k)-1)/2] are composite, excluding those primes in A080359.
A261718: Number A(n,k) of partitions of n where each part i is marked with a word of length i over a k-ary alphabet whose letters appear in alphabetical order; square array A(n,k), n>=0, k>=0, read by antidiagonals.