21030636 has 48 divisors (see below), whose sum is σ = 54069120. Its totient is φ = 6309120.

The previous prime is 21030619. The next prime is 21030637. The reversal of 21030636 is 63603012.

It is not an unprimeable number, because it can be changed into a prime (21030637) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13380 + ... + 14868.

It is an arithmetic number, because the mean of its divisors is an integer number (1126440).

Almost surely, 2^21030636 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 21030636, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27034560).

21030636 is an abundant number, since it is smaller than the sum of its proper divisors (33038484).

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

21030636 is a wasteful number, since it uses less digits than its factorization.

21030636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1614 (or 1612 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 21.

The square root of 21030636 is about 4585.9171383705. The cubic root of 21030636 is about 276.0265149910.

Adding to 21030636 its reverse (63603012), we get a palindrome (84633648).

The spelling of 21030636 in words is "twenty-one million, thirty thousand, six hundred thirty-six".