21005012 has 12 divisors (see below), whose sum is σ = 42010080. Its totient is φ = 9002136.

The previous prime is 21005009. The next prime is 21005029. The reversal of 21005012 is 21050012.

21005012 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21004984 and 21005002.

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, 375062 + ... + 375117.

It is an arithmetic number, because the mean of its divisors is an integer number (3500840).

Almost surely, 2^21005012 is an apocalyptic number.

It is an amenable number.

21005012 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21005012 is a wasteful number, since it uses less digits than its factorization.

21005012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750190 (or 750188 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 21005012 is about 4583.1225163637. The cubic root of 21005012 is about 275.9143646668.

Adding to 21005012 its reverse (21050012), we get a palindrome (42055024).

The spelling of 21005012 in words is "twenty-one million, five thousand, twelve".