21121128 has 128 divisors (see below), whose sum is σ = 68448000. Its totient is φ = 5909760.

The previous prime is 21121099. The next prime is 21121129. The reversal of 21121128 is 82112112.

It is a super-2 number, since 2×21121128² = 892204095984768, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21121128.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121129) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 92118 + ... + 92346.

It is an arithmetic number, because the mean of its divisors is an integer number (534750).

Almost surely, 2^21121128 is an apocalyptic number.

21121128 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21121128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34224000).

21121128 is an abundant number, since it is smaller than the sum of its proper divisors (47326872).

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

21121128 is a wasteful number, since it uses less digits than its factorization.

21121128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312 (or 302 counting only the distinct ones).

The product of its digits is 64, while the sum is 18.

The square root of 21121128 is about 4595.7728403393. The cubic root of 21121128 is about 276.4218501718.

It can be divided in two parts, 2112 and 1128, that added together give a triangular number (3240 = T₈₀).

The spelling of 21121128 in words is "twenty-one million, one hundred twenty-one thousand, one hundred twenty-eight".