21620320 has 48 divisors (see below), whose sum is σ = 51453360. Its totient is φ = 8584704.

The previous prime is 21620317. The next prime is 21620323. The reversal of 21620320 is 2302612.

It is an interprime number because it is at equal distance from previous prime (21620317) and next prime (21620323).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21620294 and 21620303.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620323) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25666 + ... + 26494.

It is an arithmetic number, because the mean of its divisors is an integer number (1071945).

Almost surely, 2^21620320 is an apocalyptic number.

21620320 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 21620320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25726680).

21620320 is an abundant number, since it is smaller than the sum of its proper divisors (29833040).

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

21620320 is a wasteful number, since it uses less digits than its factorization.

21620320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1007 (or 999 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21620320 is about 4649.7655854892. The cubic root of 21620320 is about 278.5826332803.

Adding to 21620320 its reverse (2302612), we get a palindrome (23922932).

The spelling of 21620320 in words is "twenty-one million, six hundred twenty thousand, three hundred twenty".