21056047 has 24 divisors (see below), whose sum is σ = 24359616. Its totient is φ = 18123264.

The previous prime is 21056039. The next prime is 21056051. The reversal of 21056047 is 74065012.

It is not a de Polignac number, because 21056047 - 2³ = 21056039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 288403 + ... + 288475.

It is an arithmetic number, because the mean of its divisors is an integer number (1014984).

Almost surely, 2^21056047 is an apocalyptic number.

21056047 is a deficient number, since it is larger than the sum of its proper divisors (3303569).

21056047 is a wasteful number, since it uses less digits than its factorization.

21056047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175 (or 156 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21056047 is about 4588.6868491977. The cubic root of 21056047 is about 276.1376431352.

The spelling of 21056047 in words is "twenty-one million, fifty-six thousand, forty-seven".