21211520 has 128 divisors (see below), whose sum is σ = 58164480. Its totient is φ = 7321600.

The previous prime is 21211507. The next prime is 21211577. The reversal of 21211520 is 2511212.

It is a tau number, because it is divible by the number of its divisors (128).

It is a junction number, because it is equal to n+sod(n) for n = 21211495 and 21211504.

It is a congruent number.

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, 161855 + ... + 161985.

It is an arithmetic number, because the mean of its divisors is an integer number (454410).

Almost surely, 2^21211520 is an apocalyptic number.

21211520 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 21211520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29082240).

21211520 is an abundant number, since it is smaller than the sum of its proper divisors (36952960).

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

21211520 is a wasteful number, since it uses less digits than its factorization.

21211520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 184 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21211520 is about 4605.5965954478. The cubic root of 21211520 is about 276.8156227608.

Adding to 21211520 its reverse (2511212), we get a palindrome (23722732).

The spelling of 21211520 in words is "twenty-one million, two hundred eleven thousand, five hundred twenty".