21047072 has 18 divisors (see below), whose sum is σ = 41487579. Its totient is φ = 10510560.

The previous prime is 21047051. The next prime is 21047077. The reversal of 21047072 is 27074012.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in only one way, i.e., 10523536 + 10523536 = 3244^2 + 3244^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3244.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21047077) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 25547 + ... + 26357.

Almost surely, 2^21047072 is an apocalyptic number.

It is an amenable number.

21047072 is a deficient number, since it is larger than the sum of its proper divisors (20440507).

21047072 is an frugal number, since it uses more digits than its factorization.

21047072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1632 (or 813 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 21047072 is about 4587.7087963383. The cubic root of 21047072 is about 276.0984036149.

The spelling of 21047072 in words is "twenty-one million, forty-seven thousand, seventy-two".