21818216 has 32 divisors (see below), whose sum is σ = 47053440. Its totient is φ = 9290688.

The previous prime is 21818207. The next prime is 21818221. The reversal of 21818216 is 61281812.

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 7 ways as a sum of consecutive naturals, for example, 8186 + ... + 10518.

It is an arithmetic number, because the mean of its divisors is an integer number (1470420).

Almost surely, 2^21818216 is an apocalyptic number.

It is an amenable number.

21818216 is an abundant number, since it is smaller than the sum of its proper divisors (25235224).

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

21818216 is a wasteful number, since it uses less digits than its factorization.

21818216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2513 (or 2509 counting only the distinct ones).

The product of its digits is 1536, while the sum is 29.

The square root of 21818216 is about 4670.9973239127. The cubic root of 21818216 is about 279.4300310326.

The spelling of 21818216 in words is "twenty-one million, eight hundred eighteen thousand, two hundred sixteen".