21047472 has 80 divisors (see below), whose sum is σ = 61246080. Its totient is φ = 6919488.

The previous prime is 21047449. The next prime is 21047527. The reversal of 21047472 is 27474012.

It is a happy number.

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, 35563 + ... + 36149.

It is an arithmetic number, because the mean of its divisors is an integer number (765576).

Almost surely, 2^21047472 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 21047472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30623040).

21047472 is an abundant number, since it is smaller than the sum of its proper divisors (40198608).

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

21047472 is a wasteful number, since it uses less digits than its factorization.

21047472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687 (or 675 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21047472 is about 4587.7523908773. The cubic root of 21047472 is about 276.1001526889.

The spelling of 21047472 in words is "twenty-one million, forty-seven thousand, four hundred seventy-two".