21236020 has 24 divisors (see below), whose sum is σ = 48026664. Its totient is φ = 7840896.

The previous prime is 21235999. The next prime is 21236021. The reversal of 21236020 is 2063212.

It can be written as a sum of positive squares in 4 ways, for example, as 39204 + 21196816 = 198^2 + 4604^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21235985 and 21236003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21236021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40579 + ... + 41098.

It is an arithmetic number, because the mean of its divisors is an integer number (2001111).

Almost surely, 2^21236020 is an apocalyptic number.

21236020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21236020 is an abundant number, since it is smaller than the sum of its proper divisors (26790644).

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

21236020 is a wasteful number, since it uses less digits than its factorization.

21236020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81699 (or 81697 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21236020 is about 4608.2556352702. The cubic root of 21236020 is about 276.9221587893.

Adding to 21236020 its reverse (2063212), we get a palindrome (23299232).

The spelling of 21236020 in words is "twenty-one million, two hundred thirty-six thousand, twenty".