21438228 has 24 divisors (see below), whose sum is σ = 57168832. Its totient is φ = 6125184.

The previous prime is 21438217. The next prime is 21438239. The reversal of 21438228 is 82283412.

It is an interprime number because it is at equal distance from previous prime (21438217) and next prime (21438239).

It is a junction number, because it is equal to n+sod(n) for n = 21438195 and 21438204.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127525 + ... + 127692.

Almost surely, 2^21438228 is an apocalyptic number.

21438228 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21438228 is an abundant number, since it is smaller than the sum of its proper divisors (35730604).

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

21438228 is a wasteful number, since it uses less digits than its factorization.

21438228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255231 (or 255229 counting only the distinct ones).

The product of its digits is 6144, while the sum is 30.

The square root of 21438228 is about 4630.1434103060. The cubic root of 21438228 is about 277.7983286247.

The spelling of 21438228 in words is "twenty-one million, four hundred thirty-eight thousand, two hundred twenty-eight".