21005016 has 16 divisors (see below), whose sum is σ = 52512600. Its totient is φ = 7001664.

The previous prime is 21005009. The next prime is 21005029. The reversal of 21005016 is 61050012.

It is a junction number, because it is equal to n+sod(n) for n = 21004986 and 21005004.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 437581 + ... + 437628.

Almost surely, 2^21005016 is an apocalyptic number.

It is an amenable number.

21005016 is an abundant number, since it is smaller than the sum of its proper divisors (31507584).

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

21005016 is a wasteful number, since it uses less digits than its factorization.

21005016 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875218 (or 875214 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21005016 is about 4583.1229527474. The cubic root of 21005016 is about 275.9143821809.

Adding to 21005016 its reverse (61050012), we get a palindrome (82055028).

The spelling of 21005016 in words is "twenty-one million, five thousand, sixteen".