18221400 has 144 divisors (see below), whose sum is σ = 62674560. Its totient is φ = 4742400.

The previous prime is 18221393. The next prime is 18221407. The reversal of 18221400 is 412281.

It is an interprime number because it is at equal distance from previous prime (18221393) and next prime (18221407).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18221407) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 95305 + ... + 95495.

It is an arithmetic number, because the mean of its divisors is an integer number (435240).

Almost surely, 2^18221400 is an apocalyptic number.

18221400 is a gapful number since it is divisible by the number (10) 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 18221400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31337280).

18221400 is an abundant number, since it is smaller than the sum of its proper divisors (44453160).

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

18221400 is a wasteful number, since it uses less digits than its factorization.

18221400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266 (or 254 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 18221400 is about 4268.6531833823. The cubic root of 18221400 is about 263.1442677856.

Adding to 18221400 its reverse (412281), we get a palindrome (18633681).

The spelling of 18221400 in words is "eighteen million, two hundred twenty-one thousand, four hundred".