21029988 has 96 divisors (see below), whose sum is σ = 59270400. Its totient is φ = 5677056.

The previous prime is 21029977. The next prime is 21030001. The reversal of 21029988 is 88992012.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 216756 + ... + 216852.

It is an arithmetic number, because the mean of its divisors is an integer number (617400).

Almost surely, 2^21029988 is an apocalyptic number.

21029988 is a gapful number since it is divisible by the number (28) 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 21029988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29635200).

21029988 is an abundant number, since it is smaller than the sum of its proper divisors (38240412).

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

21029988 is a wasteful number, since it uses less digits than its factorization.

21029988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229 (or 227 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 39.

The square root of 21029988 is about 4585.8464867459. The cubic root of 21029988 is about 276.0236799679.

It can be divided in two parts, 2102 and 9988, that added together give a triangular number (12090 = T₁₅₅).

The spelling of 21029988 in words is "twenty-one million, twenty-nine thousand, nine hundred eighty-eight".