21389228 has 12 divisors (see below), whose sum is σ = 42778512. Its totient is φ = 9166800.

The previous prime is 21389177. The next prime is 21389239. The reversal of 21389228 is 82298312.

21389228 is an admirable number.

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 381923 + ... + 381978.

It is an arithmetic number, because the mean of its divisors is an integer number (3564876).

Almost surely, 2^21389228 is an apocalyptic number.

21389228 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21389228 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21389228 is a wasteful number, since it uses less digits than its factorization.

21389228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 763912 (or 763910 counting only the distinct ones).

The product of its digits is 13824, while the sum is 35.

The square root of 21389228 is about 4624.8489705070. The cubic root of 21389228 is about 277.5865184870.

The spelling of 21389228 in words is "twenty-one million, three hundred eighty-nine thousand, two hundred twenty-eight".