21551800 has 48 divisors (see below), whose sum is σ = 50454360. Its totient is φ = 8561280.

The previous prime is 21551791. The next prime is 21551819. The reversal of 21551800 is 815512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 39127 + ... + 39673.

Almost surely, 2^21551800 is an apocalyptic number.

21551800 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 21551800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25227180).

21551800 is an abundant number, since it is smaller than the sum of its proper divisors (28902560).

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

21551800 is a wasteful number, since it uses less digits than its factorization.

21551800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 760 (or 751 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 22.

The square root of 21551800 is about 4642.3916250140. The cubic root of 21551800 is about 278.2880233493.

The spelling of 21551800 in words is "twenty-one million, five hundred fifty-one thousand, eight hundred".