21043621 has 8 divisors (see below), whose sum is σ = 22368320. Its totient is φ = 19740672.

The previous prime is 21043613. The next prime is 21043661. The reversal of 21043621 is 12634012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21043621 - 2³ = 21043613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043661) 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, 3420 + ... + 7333.

It is an arithmetic number, because the mean of its divisors is an integer number (2796040).

Almost surely, 2^21043621 is an apocalyptic number.

It is an amenable number.

21043621 is a deficient number, since it is larger than the sum of its proper divisors (1324699).

21043621 is a wasteful number, since it uses less digits than its factorization.

21043621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10875.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21043621 is about 4587.3326672479. The cubic root of 21043621 is about 276.0833125581.

Adding to 21043621 its reverse (12634012), we get a palindrome (33677633).

The spelling of 21043621 in words is "twenty-one million, forty-three thousand, six hundred twenty-one".