21405852 has 72 divisors (see below), whose sum is σ = 59439744. Its totient is φ = 6454656.

The previous prime is 21405829. The next prime is 21405871. The reversal of 21405852 is 25850412.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24373 + ... + 25235.

It is an arithmetic number, because the mean of its divisors is an integer number (825552).

Almost surely, 2^21405852 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21405852, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29719872).

21405852 is an abundant number, since it is smaller than the sum of its proper divisors (38033892).

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

21405852 is a wasteful number, since it uses less digits than its factorization.

21405852 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 939 (or 934 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 27.

The square root of 21405852 is about 4626.6458693096. The cubic root of 21405852 is about 277.6584145412.

The spelling of 21405852 in words is "twenty-one million, four hundred five thousand, eight hundred fifty-two".