16720521 has 4 divisors (see below), whose sum is σ = 22294032. Its totient is φ = 11147012.

The previous prime is 16720511. The next prime is 16720547. The reversal of 16720521 is 12502761.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12502761 = 3 ⋅4167587.

It is a cyclic number.

It is not a de Polignac number, because 16720521 - 2¹⁰ = 16719497 is a prime.

It is a super-2 number, since 2×16720521² = 559151645022882, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 16720491 and 16720500.

It is not an unprimeable number, because it can be changed into a prime (16720511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2786751 + ... + 2786756.

It is an arithmetic number, because the mean of its divisors is an integer number (5573508).

Almost surely, 2^16720521 is an apocalyptic number.

It is an amenable number.

16720521 is a deficient number, since it is larger than the sum of its proper divisors (5573511).

16720521 is an equidigital number, since it uses as much as digits as its factorization.

16720521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5573510.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 16720521 is about 4089.0733669133. The cubic root of 16720521 is about 255.7113088835.

The spelling of 16720521 in words is "sixteen million, seven hundred twenty thousand, five hundred twenty-one".