21047521 has 8 divisors (see below), whose sum is σ = 23220000. Its totient is φ = 18918240.

The previous prime is 21047449. The next prime is 21047527. The reversal of 21047521 is 12574012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21047521 - 2⁷ = 21047393 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21047492 and 21047501.

It is not an unprimeable number, because it can be changed into a prime (21047527) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9771 + ... + 11728.

It is an arithmetic number, because the mean of its divisors is an integer number (2902500).

Almost surely, 2^21047521 is an apocalyptic number.

It is an amenable number.

21047521 is a deficient number, since it is larger than the sum of its proper divisors (2172479).

21047521 is a wasteful number, since it uses less digits than its factorization.

21047521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21599.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 21047521 is about 4587.7577311798. The cubic root of 21047521 is about 276.1003669490.

The spelling of 21047521 in words is "twenty-one million, forty-seven thousand, five hundred twenty-one".