21937216 has 56 divisors (see below), whose sum is σ = 51937920. Its totient is φ = 8988672.

The previous prime is 21937213. The next prime is 21937217. The reversal of 21937216 is 61273912.

It is a tau number, because it is divible by the number of its divisors (56).

It is not an unprimeable number, because it can be changed into a prime (21937213) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 9240 + ... + 11368.

Almost surely, 2^21937216 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 21937216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25968960).

21937216 is an abundant number, since it is smaller than the sum of its proper divisors (30000704).

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

21937216 is a wasteful number, since it uses less digits than its factorization.

21937216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2171 (or 2161 counting only the distinct ones).

The product of its digits is 4536, while the sum is 31.

The square root of 21937216 is about 4683.7181811036. The cubic root of 21937216 is about 279.9371287411.

It can be divided in two parts, 2193 and 7216, that added together give a square (9409 = 97²).

The spelling of 21937216 in words is "twenty-one million, nine hundred thirty-seven thousand, two hundred sixteen".