21036820 has 48 divisors (see below), whose sum is σ = 53464320. Its totient is φ = 6787584.

The previous prime is 21036811. The next prime is 21036833. The reversal of 21036820 is 2863012.

It is a junction number, because it is equal to n+sod(n) for n = 21036791 and 21036800.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2040 + ... + 6799.

It is an arithmetic number, because the mean of its divisors is an integer number (1113840).

Almost surely, 2^21036820 is an apocalyptic number.

21036820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21036820 is an abundant number, since it is smaller than the sum of its proper divisors (32427500).

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

21036820 is a wasteful number, since it uses less digits than its factorization.

21036820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8872 (or 8870 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21036820 is about 4586.5913269006. The cubic root of 21036820 is about 276.0535672825.

Adding to 21036820 its reverse (2863012), we get a palindrome (23899832).

The spelling of 21036820 in words is "twenty-one million, thirty-six thousand, eight hundred twenty".