21005334 has 48 divisors (see below), whose sum is σ = 53134848. Its totient is φ = 5872176.

The previous prime is 21005329. The next prime is 21005339. The reversal of 21005334 is 43350012.

It is an interprime number because it is at equal distance from previous prime (21005329) and next prime (21005339).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005339) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4149 + ... + 7695.

It is an arithmetic number, because the mean of its divisors is an integer number (1106976).

Almost surely, 2^21005334 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21005334, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26567424).

21005334 is an abundant number, since it is smaller than the sum of its proper divisors (32129514).

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

21005334 is a wasteful number, since it uses less digits than its factorization.

21005334 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3609 (or 3606 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21005334 is about 4583.1576451176. The cubic root of 21005334 is about 275.9157745520.

Adding to 21005334 its reverse (43350012), we get a palindrome (64355346).

The spelling of 21005334 in words is "twenty-one million, five thousand, three hundred thirty-four".