21021012 has 48 divisors (see below), whose sum is σ = 54902400. Its totient is φ = 6955200.

The previous prime is 21021001. The next prime is 21021043. The reversal of 21021012 is 21012012.

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 = 21020985 and 21021003.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15664 + ... + 16952.

It is an arithmetic number, because the mean of its divisors is an integer number (1143800).

Almost surely, 2^21021012 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 21021012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27451200).

21021012 is an abundant number, since it is smaller than the sum of its proper divisors (33881388).

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

21021012 is a wasteful number, since it uses less digits than its factorization.

21021012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1453 (or 1445 counting only the distinct ones).

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

The square root of 21021012 is about 4584.8677189206. The cubic root of 21021012 is about 275.9844036556.

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

The spelling of 21021012 in words is "twenty-one million, twenty-one thousand, twelve".