21807216 has 60 divisors (see below), whose sum is σ = 61417200. Its totient is φ = 7223040.

The previous prime is 21807211. The next prime is 21807223. The reversal of 21807216 is 61270812.

It is a self number, because there is not a number n which added to its sum of digits gives 21807216.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21807211) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28276 + ... + 29036.

It is an arithmetic number, because the mean of its divisors is an integer number (1023620).

Almost surely, 2^21807216 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 21807216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30708600).

21807216 is an abundant number, since it is smaller than the sum of its proper divisors (39609984).

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

21807216 is a wasteful number, since it uses less digits than its factorization.

21807216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 974 (or 965 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21807216 is about 4669.8196967335. The cubic root of 21807216 is about 279.3830634431.

The spelling of 21807216 in words is "twenty-one million, eight hundred seven thousand, two hundred sixteen".