21538000 has 120 divisors (see below), whose sum is σ = 57886920. Its totient is φ = 7744000.

The previous prime is 21537979. The next prime is 21538003. The reversal of 21538000 is 83512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2944656 + 18593344 = 1716^2 + 4312^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538003) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 241956 + ... + 242044.

It is an arithmetic number, because the mean of its divisors is an integer number (482391).

Almost surely, 2^21538000 is an apocalyptic number.

21538000 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 21538000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28943460).

21538000 is an abundant number, since it is smaller than the sum of its proper divisors (36348920).

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

21538000 is a wasteful number, since it uses less digits than its factorization.

21538000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21538000 is about 4640.9050841404. The cubic root of 21538000 is about 278.2286130804.

It can be divided in two parts, 2153 and 8000, that added together give a triangular number (10153 = T₁₄₂).

The spelling of 21538000 in words is "twenty-one million, five hundred thirty-eight thousand".