21072128 has 72 divisors (see below), whose sum is σ = 52489920. Its totient is φ = 8202240.

The previous prime is 21072113. The next prime is 21072131. The reversal of 21072128 is 82127012.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19178 + ... + 20246.

Almost surely, 2^21072128 is an apocalyptic number.

21072128 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 21072128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26244960).

21072128 is an abundant number, since it is smaller than the sum of its proper divisors (31417792).

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

21072128 is a wasteful number, since it uses less digits than its factorization.

21072128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1103 (or 1089 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21072128 is about 4590.4387589859. The cubic root of 21072128 is about 276.2079228584.

The spelling of 21072128 in words is "twenty-one million, seventy-two thousand, one hundred twenty-eight".