Properties of the Number 990

Nine Hundred Ninety

Basics

Value: 989 → 990 → 991

Parity: even

Prime: No

Previous Prime: 983

Next Prime: 991

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 2 × 3 ² × 5 × 11

Divisors: 1, 2, 3, 5, 6, 9, 10, 11, 15, 18

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 1111011110

Octal: 1736

Duodecimal: 6A6

Hexadecimal: 3de

Square: 980100

Square Root: 31.464265445104548

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: No

Perfect Number: No

Special

Kaprekar Constant: No

Munchausen Constant: No

Armstrong Number: No

Kaprekar Number: No

Catalan Number: No

Vampire Number: No

Taxicab Number: No

Super Prime: No

Friedman Number: No

Fermat Number: No

Cullen Number: No

OEIS Sequences

Triangular numbers: a(n) = binomial(n+1,2) = n*(n+1)/2 = 0 + 1 + 2 + ... + n. A217

Second hexagonal numbers: a(n) = n*(2·n + 1). A14105

Numbers having k prime factors (counted with multiplicity), the largest of which is the k-th prime. A106529

a(n) = n*(n-1)*(n-2) (or n!/(n-3)!). A7531

a(n) is the largest number such that all of a(n)'s length-n substrings are distinct and divisible by 99. A93299

Number of aperiodic binary strings of length n; also number of binary sequences with primitive period n. A27375

a(n) = binomial(n,2): number of size-2 subsets of {0,1,...,n} that contain no consecutive integers. A161680

a(n) = n*(n+3). A28552

Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8. A50534

Triangle of Bessel numbers read by rows: T(n,k) is the number of k-matchings of the complete graph K(n). A100861