21106638 has 48 divisors (see below), whose sum is σ = 52715520. Its totient is φ = 5978448.

The previous prime is 21106607. The next prime is 21106643. The reversal of 21106638 is 83660112.

21106638 is a `hidden beast` number, since 21 + 1 + 0 + 6 + 638 = 666.

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 23 ways as a sum of consecutive naturals, for example, 15343 + ... + 16661.

It is an arithmetic number, because the mean of its divisors is an integer number (1098240).

Almost surely, 2^21106638 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21106638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26357760).

21106638 is an abundant number, since it is smaller than the sum of its proper divisors (31608882).

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

21106638 is a wasteful number, since it uses less digits than its factorization.

21106638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1461 (or 1458 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21106638 is about 4594.1961211947. The cubic root of 21106638 is about 276.3586232945.

The spelling of 21106638 in words is "twenty-one million, one hundred six thousand, six hundred thirty-eight".