21012012 has 72 divisors (see below), whose sum is σ = 61152000. Its totient is φ = 5959008.

The previous prime is 21011981. The next prime is 21012053. The reversal of 21012012 is 21021012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21011985 and 21012003.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49939 + ... + 50357.

Almost surely, 2^21012012 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 21012012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30576000).

21012012 is an abundant number, since it is smaller than the sum of its proper divisors (40139988).

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

21012012 is a wasteful number, since it uses less digits than its factorization.

21012012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635 (or 630 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21012012 is about 4583.8861242400. The cubic root of 21012012 is about 275.9450110992.

Adding to 21012012 its reverse (21021012), we get a palindrome (42033024).

The spelling of 21012012 in words is "twenty-one million, twelve thousand, twelve".