21236418 has 80 divisors (see below), whose sum is σ = 55454784. Its totient is φ = 5948640.

The previous prime is 21236399. The next prime is 21236419. The reversal of 21236418 is 81463212.

21236418 is a `hidden beast` number, since 2 + 12 + 3 + 641 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21236391 and 21236400.

It is not an unprimeable number, because it can be changed into a prime (21236419) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 69021 + ... + 69327.

Almost surely, 2^21236418 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21236418, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27727392).

21236418 is an abundant number, since it is smaller than the sum of its proper divisors (34218366).

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

21236418 is a wasteful number, since it uses less digits than its factorization.

21236418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 389 (or 380 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21236418 is about 4608.2988184361. The cubic root of 21236418 is about 276.9238887797.

The spelling of 21236418 in words is "twenty-one million, two hundred thirty-six thousand, four hundred eighteen".