21215236 has 45 divisors (see below), whose sum is σ = 44252999. Its totient is φ = 8898792.

The previous prime is 21215231. The next prime is 21215237. The reversal of 21215236 is 63251212.

The square root of 21215236 is 4606.

It is a perfect power (a square), and thus also a powerful number.

It is not an unprimeable number, because it can be changed into a prime (21215231) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 451365 + ... + 451411.

Almost surely, 2^21215236 is an apocalyptic number.

21215236 is the 4606-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21215236

21215236 is an abundant number, since it is smaller than the sum of its proper divisors (23037763).

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

21215236 is an frugal number, since it uses more digits than its factorization.

21215236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126 (or 56 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The cubic root of 21215236 is about 276.8317867257.

Adding to 21215236 its reverse (63251212), we get a palindrome (84466448).

The spelling of 21215236 in words is "twenty-one million, two hundred fifteen thousand, two hundred thirty-six".