21420228 has 12 divisors (see below), whose sum is σ = 49980560. Its totient is φ = 7140072.

The previous prime is 21420227. The next prime is 21420233. The reversal of 21420228 is 82202412.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21420227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 892498 + ... + 892521.

Almost surely, 2^21420228 is an apocalyptic number.

It is an amenable number.

21420228 is an abundant number, since it is smaller than the sum of its proper divisors (28560332).

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

21420228 is a wasteful number, since it uses less digits than its factorization.

21420228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1785026 (or 1785024 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 21420228 is about 4628.1992178384. The cubic root of 21420228 is about 277.7205583594.

The spelling of 21420228 in words is "twenty-one million, four hundred twenty thousand, two hundred twenty-eight".