21130720 has 48 divisors (see below), whose sum is σ = 53766720. Its totient is φ = 7801344.

The previous prime is 21130699. The next prime is 21130727. The reversal of 21130720 is 2703112.

It is a happy number.

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 = 21130694 and 21130703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21130727) 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, 3000 + ... + 7159.

It is an arithmetic number, because the mean of its divisors is an integer number (1120140).

Almost surely, 2^21130720 is an apocalyptic number.

21130720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21130720 is an abundant number, since it is smaller than the sum of its proper divisors (32636000).

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

21130720 is a wasteful number, since it uses less digits than its factorization.

21130720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10187 (or 10179 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21130720 is about 4596.8162895639. The cubic root of 21130720 is about 276.4636888007.

Adding to 21130720 its reverse (2703112), we get a palindrome (23833832).

The spelling of 21130720 in words is "twenty-one million, one hundred thirty thousand, seven hundred twenty".