21210520 has 32 divisors (see below), whose sum is σ = 47858400. Its totient is φ = 8460288.

The previous prime is 21210499. The next prime is 21210521. The reversal of 21210520 is 2501212.

It is a self number, because there is not a number n which added to its sum of digits gives 21210520.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210521) 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, 22621 + ... + 23539.

It is an arithmetic number, because the mean of its divisors is an integer number (1495575).

Almost surely, 2^21210520 is an apocalyptic number.

21210520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21210520 is an abundant number, since it is smaller than the sum of its proper divisors (26647880).

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

21210520 is a wasteful number, since it uses less digits than its factorization.

21210520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1507 (or 1503 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21210520 is about 4605.4880306000. The cubic root of 21210520 is about 276.8112726094.

Adding to 21210520 its reverse (2501212), we get a palindrome (23711732).

The spelling of 21210520 in words is "twenty-one million, two hundred ten thousand, five hundred twenty".