21172128 has 24 divisors (see below), whose sum is σ = 55577088. Its totient is φ = 7057344.

The previous prime is 21172097. The next prime is 21172133. The reversal of 21172128 is 82127112.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a junction number, because it is equal to n+sod(n) for n = 21172098 and 21172107.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110176 + ... + 110367.

It is an arithmetic number, because the mean of its divisors is an integer number (2315712).

Almost surely, 2^21172128 is an apocalyptic number.

It is an amenable number.

21172128 is an abundant number, since it is smaller than the sum of its proper divisors (34404960).

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

21172128 is a wasteful number, since it uses less digits than its factorization.

21172128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220556 (or 220548 counting only the distinct ones).

The product of its digits is 448, while the sum is 24.

The square root of 21172128 is about 4601.3180720311. The cubic root of 21172128 is about 276.6441581017.

The spelling of 21172128 in words is "twenty-one million, one hundred seventy-two thousand, one hundred twenty-eight".