21235821 has 8 divisors (see below), whose sum is σ = 28335840. Its totient is φ = 14146512.

The previous prime is 21235813. The next prime is 21235829. The reversal of 21235821 is 12853212.

It is an interprime number because it is at equal distance from previous prime (21235813) and next prime (21235829).

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

It is not a de Polignac number, because 21235821 - 2³ = 21235813 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21235791 and 21235800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21235829) 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, 5686 + ... + 8648.

It is an arithmetic number, because the mean of its divisors is an integer number (3541980).

Almost surely, 2^21235821 is an apocalyptic number.

It is an amenable number.

21235821 is a deficient number, since it is larger than the sum of its proper divisors (7100019).

21235821 is a wasteful number, since it uses less digits than its factorization.

21235821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5355.

The product of its digits is 960, while the sum is 24.

The square root of 21235821 is about 4608.2340435355. The cubic root of 21235821 is about 276.9212937860.

The spelling of 21235821 in words is "twenty-one million, two hundred thirty-five thousand, eight hundred twenty-one".