21009132 has 60 divisors (see below), whose sum is σ = 55874896. Its totient is φ = 6881760.

The previous prime is 21009091. The next prime is 21009139. The reversal of 21009132 is 23190012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21009139) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 19233 + ... + 20295.

Almost surely, 2^21009132 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 21009132, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27937448).

21009132 is an abundant number, since it is smaller than the sum of its proper divisors (34865764).

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

21009132 is a wasteful number, since it uses less digits than its factorization.

21009132 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1140 (or 1129 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21009132 is about 4583.5719695451. The cubic root of 21009132 is about 275.9324031055.

Adding to 21009132 its reverse (23190012), we get a palindrome (44199144).

The spelling of 21009132 in words is "twenty-one million, nine thousand, one hundred thirty-two".