21131838 has 144 divisors (see below), whose sum is σ = 60999120. Its totient is φ = 5225472.

The previous prime is 21131827. The next prime is 21131881. The reversal of 21131838 is 83813112.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 217806 + ... + 217902.

It is an arithmetic number, because the mean of its divisors is an integer number (423605).

Almost surely, 2^21131838 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21131838, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30499560).

21131838 is an abundant number, since it is smaller than the sum of its proper divisors (39867282).

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

21131838 is a wasteful number, since it uses less digits than its factorization.

21131838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 141 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21131838 is about 4596.9378938593. The cubic root of 21131838 is about 276.4685644976.

The spelling of 21131838 in words is "twenty-one million, one hundred thirty-one thousand, eight hundred thirty-eight".