21217072 has 40 divisors (see below), whose sum is σ = 43925760. Its totient is φ = 9898560.

The previous prime is 21217039. The next prime is 21217087. The reversal of 21217072 is 27071212.

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, 21093 + ... + 22075.

It is an arithmetic number, because the mean of its divisors is an integer number (1098144).

Almost surely, 2^21217072 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 21217072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21962880).

21217072 is an abundant number, since it is smaller than the sum of its proper divisors (22708688).

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

21217072 is a wasteful number, since it uses less digits than its factorization.

21217072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1081 (or 1075 counting only the distinct ones).

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 21217072 is about 4606.1993009422. The cubic root of 21217072 is about 276.8397723152.

Adding to 21217072 its reverse (27071212), we get a palindrome (48288284).

The spelling of 21217072 in words is "twenty-one million, two hundred seventeen thousand, seventy-two".