21821238 has 20 divisors (see below), whose sum is σ = 48896100. Its totient is φ = 7273692.

The previous prime is 21821237. The next prime is 21821243. The reversal of 21821238 is 83212812.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821237) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 67188 + ... + 67511.

It is an arithmetic number, because the mean of its divisors is an integer number (2444805).

Almost surely, 2^21821238 is an apocalyptic number.

21821238 is an abundant number, since it is smaller than the sum of its proper divisors (27074862).

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

21821238 is a wasteful number, since it uses less digits than its factorization.

21821238 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134713 (or 134704 counting only the distinct ones).

The product of its digits is 1536, while the sum is 27.

The square root of 21821238 is about 4671.3207982326. The cubic root of 21821238 is about 279.4429315461.

The spelling of 21821238 in words is "twenty-one million, eight hundred twenty-one thousand, two hundred thirty-eight".