21140028 has 144 divisors (see below), whose sum is σ = 68490240. Its totient is φ = 5552064.

The previous prime is 21140011. The next prime is 21140033. The reversal of 21140028 is 82004112.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 88333 + ... + 88571.

Almost surely, 2^21140028 is an apocalyptic number.

21140028 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 21140028, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34245120).

21140028 is an abundant number, since it is smaller than the sum of its proper divisors (47350212).

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

21140028 is a wasteful number, since it uses less digits than its factorization.

21140028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 278 (or 264 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21140028 is about 4597.8286179456. The cubic root of 21140028 is about 276.5042765684.

The spelling of 21140028 in words is "twenty-one million, one hundred forty thousand, twenty-eight".