9919999 has 4 divisors (see below), whose sum is σ = 9955336. Its totient is φ = 9884664.

The previous prime is 9919997. The next prime is 9920021. The reversal of 9919999 is 9999199.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 9919999 - 2¹ = 9919997 is a prime.

It is a Duffinian number.

9919999 is a modest number, since divided by 9999 gives 991 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9919997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17244 + ... + 17809.

It is an arithmetic number, because the mean of its divisors is an integer number (2488834).

Almost surely, 2^9919999 is an apocalyptic number.

9919999 is a deficient number, since it is larger than the sum of its proper divisors (35337).

9919999 is a wasteful number, since it uses less digits than its factorization.

9919999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35336.

The product of its digits is 531441, while the sum is 55.

The square root of 9919999 is about 3149.6029908546. The cubic root of 9919999 is about 214.8674069778.

The spelling of 9919999 in words is "nine million, nine hundred nineteen thousand, nine hundred ninety-nine".