21428556 has 12 divisors (see below), whose sum is σ = 49999992. Its totient is φ = 7142848.

The previous prime is 21428549. The next prime is 21428579. The reversal of 21428556 is 65582412.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 892845 + ... + 892868.

It is an arithmetic number, because the mean of its divisors is an integer number (4166666).

Almost surely, 2^21428556 is an apocalyptic number.

It is an amenable number.

21428556 is an abundant number, since it is smaller than the sum of its proper divisors (28571436).

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

21428556 is a wasteful number, since it uses less digits than its factorization.

21428556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1785720 (or 1785718 counting only the distinct ones).

The product of its digits is 19200, while the sum is 33.

The square root of 21428556 is about 4629.0988323863. The cubic root of 21428556 is about 277.7565454823.

The spelling of 21428556 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred fifty-six".