6720521 has 4 divisors (see below), whose sum is σ = 6937344. Its totient is φ = 6503700.

The previous prime is 6720517. The next prime is 6720523. The reversal of 6720521 is 1250276.

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.

It is a cyclic number.

It is not a de Polignac number, because 6720521 - 2² = 6720517 is a prime.

It is a super-2 number, since 2×6720521² = 90330805022882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6720523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108365 + ... + 108426.

It is an arithmetic number, because the mean of its divisors is an integer number (1734336).

Almost surely, 2^6720521 is an apocalyptic number.

It is an amenable number.

6720521 is a deficient number, since it is larger than the sum of its proper divisors (216823).

6720521 is a wasteful number, since it uses less digits than its factorization.

6720521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216822.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 6720521 is about 2592.3967674721. The cubic root of 6720521 is about 188.7126359092.

Adding to 6720521 its reverse (1250276), we get a palindrome (7970797).

The spelling of 6720521 in words is "six million, seven hundred twenty thousand, five hundred twenty-one".