21229218 has 48 divisors (see below), whose sum is σ = 48372480. Its totient is φ = 6719328.

The previous prime is 21229199. The next prime is 21229237. The reversal of 21229218 is 81292212.

It is an interprime number because it is at equal distance from previous prime (21229199) and next prime (21229237).

It is a junction number, because it is equal to n+sod(n) for n = 21229191 and 21229200.

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 23 ways as a sum of consecutive naturals, for example, 34671 + ... + 35277.

It is an arithmetic number, because the mean of its divisors is an integer number (1007760).

Almost surely, 2^21229218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21229218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24186240).

21229218 is an abundant number, since it is smaller than the sum of its proper divisors (27143262).

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

21229218 is a wasteful number, since it uses less digits than its factorization.

21229218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 711 (or 708 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21229218 is about 4607.5175528694. The cubic root of 21229218 is about 276.8925891293.

The spelling of 21229218 in words is "twenty-one million, two hundred twenty-nine thousand, two hundred eighteen".