21389616 has 80 divisors (see below), whose sum is σ = 62396800. Its totient is φ = 7013952.

The previous prime is 21389593. The next prime is 21389629. The reversal of 21389616 is 61698312.

21389616 is a `hidden beast` number, since 2 + 1 + 38 + 9 + 616 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28575 + ... + 29313.

It is an arithmetic number, because the mean of its divisors is an integer number (779960).

Almost surely, 2^21389616 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 21389616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31198400).

21389616 is an abundant number, since it is smaller than the sum of its proper divisors (41007184).

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

21389616 is a wasteful number, since it uses less digits than its factorization.

21389616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 823 (or 811 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 21389616 is about 4624.8909176325. The cubic root of 21389616 is about 277.5881969474.

The spelling of 21389616 in words is "twenty-one million, three hundred eighty-nine thousand, six hundred sixteen".