21634320 has 80 divisors (see below), whose sum is σ = 67763520. Its totient is φ = 5709312.

The previous prime is 21634309. The next prime is 21634337. The reversal of 21634320 is 2343612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25747 + ... + 26573.

It is an arithmetic number, because the mean of its divisors is an integer number (847044).

Almost surely, 2^21634320 is an apocalyptic number.

21634320 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 21634320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33881760).

21634320 is an abundant number, since it is smaller than the sum of its proper divisors (46129200).

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

21634320 is a wasteful number, since it uses less digits than its factorization.

21634320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 952 (or 946 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 21634320 is about 4651.2707940949. The cubic root of 21634320 is about 278.6427513441.

Adding to 21634320 its reverse (2343612), we get a palindrome (23977932).

The spelling of 21634320 in words is "twenty-one million, six hundred thirty-four thousand, three hundred twenty".