21371550 has 96 divisors (see below), whose sum is σ = 58255200. Its totient is φ = 5178880.

The previous prime is 21371509. The next prime is 21371551. The reversal of 21371550 is 5517312.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21371550.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21371551) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 736936 + ... + 736964.

It is an arithmetic number, because the mean of its divisors is an integer number (606825).

Almost surely, 2^21371550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21371550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29127600).

21371550 is an abundant number, since it is smaller than the sum of its proper divisors (36883650).

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

21371550 is a wasteful number, since it uses less digits than its factorization.

21371550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95 (or 56 counting only the distinct ones).

The product of its (nonzero) digits is 1050, while the sum is 24.

The square root of 21371550 is about 4622.9373779016. The cubic root of 21371550 is about 277.5100231750.

Adding to 21371550 its reverse (5517312), we get a palindrome (26888862).

The spelling of 21371550 in words is "twenty-one million, three hundred seventy-one thousand, five hundred fifty".