21021550 has 48 divisors (see below), whose sum is σ = 43849872. Its totient is φ = 7430400.

The previous prime is 21021529. The next prime is 21021569. The reversal of 21021550 is 5512012.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 19834 + ... + 20866.

It is an arithmetic number, because the mean of its divisors is an integer number (913539).

Almost surely, 2^21021550 is an apocalyptic number.

21021550 is an abundant number, since it is smaller than the sum of its proper divisors (22828322).

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

21021550 is a wasteful number, since it uses less digits than its factorization.

21021550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1093 (or 1088 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21021550 is about 4584.9263898126. The cubic root of 21021550 is about 275.9867580989.

Adding to 21021550 its reverse (5512012), we get a palindrome (26533562).

The spelling of 21021550 in words is "twenty-one million, twenty-one thousand, five hundred fifty".