9991664 has 10 divisors (see below), whose sum is σ = 19358880. Its totient is φ = 4995824.

The previous prime is 9991649. The next prime is 9991669. The reversal of 9991664 is 4661999.

9991664 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 312224 + ... + 312255.

It is an arithmetic number, because the mean of its divisors is an integer number (1935888).

Almost surely, 2^9991664 is an apocalyptic number.

It is an amenable number.

9991664 is a deficient number, since it is larger than the sum of its proper divisors (9367216).

9991664 is a wasteful number, since it uses less digits than its factorization.

9991664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624487 (or 624481 counting only the distinct ones).

The product of its digits is 104976, while the sum is 44.

The square root of 9991664 is about 3160.9593480461. The cubic root of 9991664 is about 215.3835878025.

The spelling of 9991664 in words is "nine million, nine hundred ninety-one thousand, six hundred sixty-four".