21021000 has 384 divisors, whose sum is σ = 89631360. Its totient is φ = 4032000.

The previous prime is 21020971. The next prime is 21021001. The reversal of 21021000 is 12012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21021000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021001) 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 95 ways as a sum of consecutive naturals, for example, 1616994 + ... + 1617006.

It is an arithmetic number, because the mean of its divisors is an integer number (233415).

Almost surely, 2^21021000 is an apocalyptic number.

21021000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21021000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44815680).

21021000 is an abundant number, since it is smaller than the sum of its proper divisors (68610360).

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

21021000 is a wasteful number, since it uses less digits than its factorization.

21021000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62 (or 41 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 21021000 is about 4584.8664102676. The cubic root of 21021000 is about 275.9843511396.

Adding to 21021000 its reverse (12012), we get a palindrome (21033012).

It can be divided in two parts, 210 and 21000, that multiplied together give a square (4410000 = 2100²).

The spelling of 21021000 in words is "twenty-one million, twenty-one thousand".