Number of the day: 4781

Paul Erös was born on this day 108 years ago.

Properties of the number 4781:

4781 is a cyclic number.
4781 = 7 × 683 is semiprime and squarefree.
4781 has 2 distinct prime factors, 4 divisors, 7 antidivisors and 4092 totatives.
4781 has an oblong digit sum 20 in base 10.
Reversing the decimal digits of 4781 results in an emirpimes.
4781 = 2391² - 2390² = 345² - 338² is the difference of 2 nonnegative squares in 2 ways.
4781 is the sum of 2 positive triangular numbers.
4781 is the difference of 2 positive pentagonal numbers in 2 ways.
4781 = 6² + 11² + 68² is the sum of 3 positive squares.
4781² is the sum of 3 positive squares.
4781 is a proper divisor of 1367³ - 1.
4781 = '4' + '781' is the concatenation of 2 semiprime numbers.
4781 is an emirpimes in (at least) the following bases: 3, 5, 9, 10, 11, 12, 14, 15, 16, 20, 21, 28, 29, 31, 40, 41, 43, 44, 49, 50, 53, 54, 55, 59, 63, 64, 65, 67, 70, 74, 80, 81, 83, 85, 88, 90, 91, 95, 96, and 98.
4781 is palindromic in (at least) the following bases: -2, and -59.
4781 in base 34 = 44l and consists of only the digits '4' and 'l'.

The number 4781 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A000100: a(n) is the number of compositions of n in which the maximal part is 3.
A005424: Smallest number that requires n iterations of the bi-unitary totient function (A116550) to reach 1.
A025415: Least sum of 3 distinct nonzero squares in exactly n ways.
A092666: a(n) = number of Egyptian fractions 1 = 1/x_1 + ... + 1/x_k (for any k), with 0 < x_1 <= ... <= x_k = n.
A116459: Numbers n such that the minimal length of the corresponding shortest addition chain A003313(n)=A003313(3*n).
A140749: Table c(n,k) of the numerators of coefficients [x^k] P(n,x) of the polynomials P(n,x) of A129891.
A240495: Number of partitions p of n such that the multiplicity of (max(p) - min(p)) is a part.
A244803: The 360 degree spoke (or ray) of a hexagonal spiral of Ulam.
A257462: Number A(n,k) of factorizations of m^n into n factors, where m is a product of exactly k distinct primes and each factor is a product of k primes (counted with multiplicity); square array A(n,k), n>=0, k>=0, read by antidiagonals.
A300937: T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 2, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.