21205632 has 160 divisors (see below), whose sum is σ = 68568480. Its totient is φ = 5795328.

The previous prime is 21205621. The next prime is 21205633. The reversal of 21205632 is 23650212.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21205599 and 21205608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205633) 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, 921973 + ... + 921995.

It is an arithmetic number, because the mean of its divisors is an integer number (428553).

Almost surely, 2^21205632 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 21205632, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34284240).

21205632 is an abundant number, since it is smaller than the sum of its proper divisors (47362848).

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

21205632 is an frugal number, since it uses more digits than its factorization.

21205632 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68 (or 35 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21205632 is about 4604.9573287925. The cubic root of 21205632 is about 276.7900071014.

Adding to 21205632 its reverse (23650212), we get a palindrome (44855844).

The spelling of 21205632 in words is "twenty-one million, two hundred five thousand, six hundred thirty-two".