21000216 has 32 divisors (see below), whose sum is σ = 52743600. Its totient is φ = 6967680.

The previous prime is 21000193. The next prime is 21000229. The reversal of 21000216 is 61200012.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3586 + ... + 7406.

Almost surely, 2^21000216 is an apocalyptic number.

It is an amenable number.

21000216 is an abundant number, since it is smaller than the sum of its proper divisors (31743384).

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

21000216 is a wasteful number, since it uses less digits than its factorization.

21000216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4059 (or 4055 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21000216 is about 4582.5992624274. The cubic root of 21000216 is about 275.8933635517.

Adding to 21000216 its reverse (61200012), we get a palindrome (82200228).

The spelling of 21000216 in words is "twenty-one million, two hundred sixteen", and thus it is an aban number.