21155472 has 80 divisors (see below), whose sum is σ = 65412480. Its totient is φ = 6507648.

The previous prime is 21155447. The next prime is 21155501. The reversal of 21155472 is 27455112.

21155472 is a `hidden beast` number, since 2 + 115 + 547 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3733 + ... + 7499.

It is an arithmetic number, because the mean of its divisors is an integer number (817656).

Almost surely, 2^21155472 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21155472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32706240).

21155472 is an abundant number, since it is smaller than the sum of its proper divisors (44257008).

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

21155472 is a wasteful number, since it uses less digits than its factorization.

21155472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3797 (or 3785 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 21155472 is about 4599.5077997542. The cubic root of 21155472 is about 276.5715942427.

The spelling of 21155472 in words is "twenty-one million, one hundred fifty-five thousand, four hundred seventy-two".