21005412 has 48 divisors (see below), whose sum is σ = 51979200. Its totient is φ = 6583680.

The previous prime is 21005401. The next prime is 21005423. The reversal of 21005412 is 21450012.

It is an interprime number because it is at equal distance from previous prime (21005401) and next prime (21005423).

It is a junction number, because it is equal to n+sod(n) for n = 21005391 and 21005400.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 41014 + ... + 41522.

It is an arithmetic number, because the mean of its divisors is an integer number (1082900).

Almost surely, 2^21005412 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 21005412, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25989600).

21005412 is an abundant number, since it is smaller than the sum of its proper divisors (30973788).

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

21005412 is a wasteful number, since it uses less digits than its factorization.

21005412 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 716 (or 714 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21005412 is about 4583.1661545268. The cubic root of 21005412 is about 275.9161160749.

Adding to 21005412 its reverse (21450012), we get a palindrome (42455424).

The spelling of 21005412 in words is "twenty-one million, five thousand, four hundred twelve".