21006016 has 56 divisors (see below), whose sum is σ = 45262800. Its totient is φ = 9633792.

The previous prime is 21005987. The next prime is 21006017. The reversal of 21006016 is 61060012.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is not an unprimeable number, because it can be changed into a prime (21006017) 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 7 ways as a sum of consecutive naturals, for example, 46560 + ... + 47008.

Almost surely, 2^21006016 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 21006016, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22631400).

21006016 is an abundant number, since it is smaller than the sum of its proper divisors (24256784).

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

21006016 is a wasteful number, since it uses less digits than its factorization.

21006016 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521 (or 511 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21006016 is about 4583.2320473657. The cubic root of 21006016 is about 275.9187606590.

Adding to 21006016 its reverse (61060012), we get a palindrome (82066028).

The spelling of 21006016 in words is "twenty-one million, six thousand, sixteen".