21818550 has 96 divisors (see below), whose sum is σ = 59496192. Its totient is φ = 5258880.

The previous prime is 21818539. The next prime is 21818557. The reversal of 21818550 is 5581812.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21818557) 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, 130567 + ... + 130733.

It is an arithmetic number, because the mean of its divisors is an integer number (619752).

Almost surely, 2^21818550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21818550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29748096).

21818550 is an abundant number, since it is smaller than the sum of its proper divisors (37677642).

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

21818550 is a wasteful number, since it uses less digits than its factorization.

21818550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262 (or 257 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 30.

The square root of 21818550 is about 4671.0330763119. The cubic root of 21818550 is about 279.4314568925.

It can be divided in two parts, 2181 and 8550, that added together give a triangular number (10731 = T₁₄₆).

The spelling of 21818550 in words is "twenty-one million, eight hundred eighteen thousand, five hundred fifty".