21399396 has 48 divisors (see below), whose sum is σ = 55661760. Its totient is φ = 6359040.

The previous prime is 21399353. The next prime is 21399401. The reversal of 21399396 is 69399312.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1116 + ... + 6636.

It is an arithmetic number, because the mean of its divisors is an integer number (1159620).

Almost surely, 2^21399396 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21399396, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27830880).

21399396 is an abundant number, since it is smaller than the sum of its proper divisors (34262364).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21399396 is a wasteful number, since it uses less digits than its factorization.

21399396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5564 (or 5562 counting only the distinct ones).

The product of its digits is 78732, while the sum is 42.

The square root of 21399396 is about 4625.9481190346. The cubic root of 21399396 is about 277.6304978300.

The spelling of 21399396 in words is "twenty-one million, three hundred ninety-nine thousand, three hundred ninety-six".