21921216 has 112 divisors (see below), whose sum is σ = 62423040. Its totient is φ = 6773760.

The previous prime is 21921191. The next prime is 21921227. The reversal of 21921216 is 61212912.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 172545 + ... + 172671.

Almost surely, 2^21921216 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 21921216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31211520).

21921216 is an abundant number, since it is smaller than the sum of its proper divisors (40501824).

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

21921216 is a wasteful number, since it uses less digits than its factorization.

21921216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 202 (or 192 counting only the distinct ones).

The product of its digits is 432, while the sum is 24.

The square root of 21921216 is about 4682.0098248509. The cubic root of 21921216 is about 279.8690544174.

The spelling of 21921216 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred sixteen".