9919 has 8 divisors (see below), whose sum is σ = 12320. Its totient is φ = 7776.

The previous prime is 9907. The next prime is 9923. The reversal of 9919 is 9199.

9919 is nontrivially palindromic in base 9.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 5-Lehmer number, since φ(9919) divides (9919-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 9919 - 2⁵ = 9887 is a prime.

It is a super-2 number, since 2×9919² = 196773122, which contains 22 as substring.

It is an Ulam number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37 + ... + 145.

It is an arithmetic number, because the mean of its divisors is an integer number (1540).

2⁹⁹¹⁹ is an apocalyptic number.

9919 is the 58-th hex number.

9919 is a deficient number, since it is larger than the sum of its proper divisors (2401).

9919 is a wasteful number, since it uses less digits than its factorization.

9919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129.

The product of its digits is 729, while the sum is 28.

The square root of 9919 is about 99.5941765366. The cubic root of 9919 is about 21.4860193948.

Adding to 9919 its product of digits (729), we get a cube (10648 = 22³).

It can be divided in two parts, 991 and 9, that added together give a cube (1000 = 10³).

The spelling of 9919 in words is "nine thousand, nine hundred nineteen".