21187236 has 96 divisors (see below), whose sum is σ = 61592832. Its totient is φ = 5529600.

The previous prime is 21187217. The next prime is 21187241. The reversal of 21187236 is 63278112.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 52636 + ... + 53036.

It is an arithmetic number, because the mean of its divisors is an integer number (641592).

Almost surely, 2^21187236 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 21187236, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30796416).

21187236 is an abundant number, since it is smaller than the sum of its proper divisors (40405596).

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

21187236 is a wasteful number, since it uses less digits than its factorization.

21187236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 469 (or 467 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 21187236 is about 4602.9594827676. The cubic root of 21187236 is about 276.7099450047.

The spelling of 21187236 in words is "twenty-one million, one hundred eighty-seven thousand, two hundred thirty-six".