9999999 has 12 divisors (see below), whose sum is σ = 14508000. Its totient is φ = 6637344.

The previous prime is 9999991. The next prime is 10000019.

9999999 is nontrivially palindromic in base 10.

It is a Cunningham number, because it is equal to 10⁷-1.

It is a trimorphic number since its cube, 999999700000029999999, ends in 9999999.

It is not a de Polignac number, because 9999999 - 2³ = 9999991 is a prime.

It is a nude number because it is divisible by every one of its digits.

It is an Ulam number.

9999999 is a modest number, since divided by 9999 gives 999 as remainder.

9999999 is a nontrivial repdigit in base 10.

It is a plaindrome in base 10.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9999991) by changing a digit.

It is a Kaprekar number, because its square (99999980000001) can be partitioned into two parts whose sum is 9999999.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 174 + ... + 4475.

It is an arithmetic number, because the mean of its divisors is an integer number (1209000).

Almost surely, 2^9999999 is an apocalyptic number.

9999999 is a deficient number, since it is larger than the sum of its proper divisors (4508001).

9999999 is a wasteful number, since it uses less digits than its factorization.

9999999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4894 (or 4891 counting only the distinct ones).

The product of its digits is 4782969, while the sum is 63.

The square root of 9999999 is about 3162.2775020545. The cubic root of 9999999 is about 215.4434618217.

The spelling of 9999999 in words is "nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine".