21217152 has 64 divisors (see below), whose sum is σ = 61493760. Its totient is φ = 6428160.

The previous prime is 21217151. The next prime is 21217159. The reversal of 21217152 is 25171212.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21217152² = 900335077982208, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217151) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1713 + ... + 6735.

It is an arithmetic number, because the mean of its divisors is an integer number (960840).

Almost surely, 2^21217152 is an apocalyptic number.

21217152 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21217152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30746880).

21217152 is an abundant number, since it is smaller than the sum of its proper divisors (40276608).

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

21217152 is a wasteful number, since it uses less digits than its factorization.

21217152 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5051 (or 5039 counting only the distinct ones).

The product of its digits is 280, while the sum is 21.

The square root of 21217152 is about 4606.2079848830. The cubic root of 21217152 is about 276.8401202607.

Adding to 21217152 its reverse (25171212), we get a palindrome (46388364).

The spelling of 21217152 in words is "twenty-one million, two hundred seventeen thousand, one hundred fifty-two".