21618212 has 72 divisors (see below), whose sum is σ = 49488768. Its totient is φ = 8164800.

The previous prime is 21618209. The next prime is 21618221. The reversal of 21618212 is 21281612.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 79637 + ... + 79907.

It is an arithmetic number, because the mean of its divisors is an integer number (687344).

Almost surely, 2^21618212 is an apocalyptic number.

21618212 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 21618212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24744384).

21618212 is an abundant number, since it is smaller than the sum of its proper divisors (27870556).

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

21618212 is a wasteful number, since it uses less digits than its factorization.

21618212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 337 (or 328 counting only the distinct ones).

The product of its digits is 384, while the sum is 23.

The square root of 21618212 is about 4649.5389018697. The cubic root of 21618212 is about 278.5735789697.

Adding to 21618212 its reverse (21281612), we get a palindrome (42899824).

The spelling of 21618212 in words is "twenty-one million, six hundred eighteen thousand, two hundred twelve".