12399921 has 24 divisors (see below), whose sum is σ = 19206720. Its totient is φ = 7688736.

The previous prime is 12399901. The next prime is 12399923. The reversal of 12399921 is 12999321.

It is a happy number.

It is not a de Polignac number, because 12399921 - 2⁶ = 12399857 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12399923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6850 + ... + 8468.

It is an arithmetic number, because the mean of its divisors is an integer number (800280).

Almost surely, 2^12399921 is an apocalyptic number.

It is an amenable number.

12399921 is a deficient number, since it is larger than the sum of its proper divisors (6806799).

12399921 is a wasteful number, since it uses less digits than its factorization.

12399921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1685 (or 1682 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 12399921 is about 3521.3521550677. The cubic root of 12399921 is about 231.4584139125.

The spelling of 12399921 in words is "twelve million, three hundred ninety-nine thousand, nine hundred twenty-one".