21072186 has 36 divisors (see below), whose sum is σ = 47749338. Its totient is φ = 6715632.

The previous prime is 21072169. The next prime is 21072187. The reversal of 21072186 is 68127012.

It can be written as a sum of positive squares in only one way, i.e., 11431161 + 9641025 = 3381^2 + 3105^2 .

It is not an unprimeable number, because it can be changed into a prime (21072187) 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, 8416 + ... + 10628.

Almost surely, 2^21072186 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21072186, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23874669).

21072186 is an abundant number, since it is smaller than the sum of its proper divisors (26677152).

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

21072186 is a wasteful number, since it uses less digits than its factorization.

21072186 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2267 (or 2241 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21072186 is about 4590.4450764605. The cubic root of 21072186 is about 276.2081762744.

Adding to 21072186 its reverse (68127012), we get a palindrome (89199198).

The spelling of 21072186 in words is "twenty-one million, seventy-two thousand, one hundred eighty-six".