21553400 has 96 divisors (see below), whose sum is σ = 55777680. Its totient is φ = 7680000.

The previous prime is 21553393. The next prime is 21553403. The reversal of 21553400 is 435512.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553403) 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 23 ways as a sum of consecutive naturals, for example, 213350 + ... + 213450.

Almost surely, 2^21553400 is an apocalyptic number.

21553400 is a gapful number since it is divisible by the number (20) 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 21553400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27888840).

21553400 is an abundant number, since it is smaller than the sum of its proper divisors (34224280).

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

21553400 is a wasteful number, since it uses less digits than its factorization.

21553400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 225 (or 216 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 20.

The square root of 21553400 is about 4642.5639467863. The cubic root of 21553400 is about 278.2949098556.

Adding to 21553400 its reverse (435512), we get a palindrome (21988912).

It can be divided in two parts, 2155 and 3400, that added together give a palindrome (5555).

The spelling of 21553400 in words is "twenty-one million, five hundred fifty-three thousand, four hundred".