21033621 has 32 divisors (see below), whose sum is σ = 35974400. Its totient is φ = 11897280.

The previous prime is 21033601. The next prime is 21033631. The reversal of 21033621 is 12633012.

21033621 is a `hidden beast` number, since 2 + 10 + 33 + 621 = 666.

It is not a de Polignac number, because 21033621 - 2⁶ = 21033557 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21033594 and 21033603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21033601) 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 31 ways as a sum of consecutive naturals, for example, 20091 + ... + 21111.

It is an arithmetic number, because the mean of its divisors is an integer number (1124200).

Almost surely, 2^21033621 is an apocalyptic number.

21033621 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21033621 is a deficient number, since it is larger than the sum of its proper divisors (14940779).

21033621 is a wasteful number, since it uses less digits than its factorization.

21033621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1146 (or 1140 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21033621 is about 4586.2425797160. The cubic root of 21033621 is about 276.0395737206.

Adding to 21033621 its reverse (12633012), we get a palindrome (33666633).

The spelling of 21033621 in words is "twenty-one million, thirty-three thousand, six hundred twenty-one".