21638133 has 24 divisors (see below), whose sum is σ = 34384896. Its totient is φ = 13003200.

The previous prime is 21638129. The next prime is 21638143. The reversal of 21638133 is 33183612.

It is a happy number.

21638133 is a `hidden beast` number, since 21 + 638 + 1 + 3 + 3 = 666.

It is not a de Polignac number, because 21638133 - 2² = 21638129 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21638097 and 21638106.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21638143) 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, 11713 + ... + 13433.

It is an arithmetic number, because the mean of its divisors is an integer number (1432704).

Almost surely, 2^21638133 is an apocalyptic number.

It is an amenable number.

21638133 is a deficient number, since it is larger than the sum of its proper divisors (12746763).

21638133 is a wasteful number, since it uses less digits than its factorization.

21638133 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1865 (or 1862 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 21638133 is about 4651.6806640181. The cubic root of 21638133 is about 278.6591204342.

It can be divided in two parts, 2163 and 8133, that added together give a triangular number (10296 = T₁₄₃).

The spelling of 21638133 in words is "twenty-one million, six hundred thirty-eight thousand, one hundred thirty-three".