21889728 has 168 divisors, whose sum is σ = 73700640. Its totient is φ = 6082560.

The previous prime is 21889717. The next prime is 21889741. The reversal of 21889728 is 82798812.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (168).

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

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 245908 + ... + 245996.

Almost surely, 2^21889728 is an apocalyptic number.

21889728 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 21889728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36850320).

21889728 is an abundant number, since it is smaller than the sum of its proper divisors (51810912).

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

21889728 is a wasteful number, since it uses less digits than its factorization.

21889728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 175 (or 162 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The square root of 21889728 is about 4678.6459579669. The cubic root of 21889728 is about 279.7349873468.

The spelling of 21889728 in words is "twenty-one million, eight hundred eighty-nine thousand, seven hundred twenty-eight".