21051228 has 48 divisors (see below), whose sum is σ = 54149760. Its totient is φ = 6312000.

The previous prime is 21051203. The next prime is 21051241. The reversal of 21051228 is 82215012.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12543 + ... + 14121.

It is an arithmetic number, because the mean of its divisors is an integer number (1128120).

Almost surely, 2^21051228 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21051228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27074880).

21051228 is an abundant number, since it is smaller than the sum of its proper divisors (33098532).

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

21051228 is a wasteful number, since it uses less digits than its factorization.

21051228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1698 (or 1696 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 21051228 is about 4588.1617233921. The cubic root of 21051228 is about 276.1165754132.

It can be divided in two parts, 2105 and 1228, that added together give a palindrome (3333).

The spelling of 21051228 in words is "twenty-one million, fifty-one thousand, two hundred twenty-eight".