21636020 has 24 divisors (see below), whose sum is σ = 51926784. Its totient is φ = 7418016.

The previous prime is 21636007. The next prime is 21636023. The reversal of 21636020 is 2063612.

It is a super-2 number, since 2×21636020² = 936234722880800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21635983 and 21636001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77132 + ... + 77411.

It is an arithmetic number, because the mean of its divisors is an integer number (2163616).

Almost surely, 2^21636020 is an apocalyptic number.

21636020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21636020 is an abundant number, since it is smaller than the sum of its proper divisors (30290764).

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

21636020 is a wasteful number, since it uses less digits than its factorization.

21636020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154559 (or 154557 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 21636020 is about 4651.4535362615. The cubic root of 21636020 is about 278.6500496287.

21636020 divided by its sum of digits (20) gives a palindrome (1081801).

Adding to 21636020 its reverse (2063612), we get a palindrome (23699632).

The spelling of 21636020 in words is "twenty-one million, six hundred thirty-six thousand, twenty".