21205152 has 108 divisors (see below), whose sum is σ = 63238266. Its totient is φ = 6998400.

The previous prime is 21205139. The next prime is 21205157. The reversal of 21205152 is 25150212.

It can be written as a sum of positive squares in only one way, i.e., 12702096 + 8503056 = 3564^2 + 2916^2 .

It is a tau number, because it is divible by the number of its divisors (108).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21205157) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 209902 + ... + 210002.

Almost surely, 2^21205152 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 21205152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31619133).

21205152 is an abundant number, since it is smaller than the sum of its proper divisors (42033114).

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

21205152 is an frugal number, since it uses more digits than its factorization.

21205152 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135 (or 106 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21205152 is about 4604.9052107508. The cubic root of 21205152 is about 276.7879186592.

Adding to 21205152 its reverse (25150212), we get a palindrome (46355364).

The spelling of 21205152 in words is "twenty-one million, two hundred five thousand, one hundred fifty-two".