6720921 has 16 divisors (see below), whose sum is σ = 10009600. Its totient is φ = 4456944.

The previous prime is 6720911. The next prime is 6720929. The reversal of 6720921 is 1290276.

It is not a de Polignac number, because 6720921 - 2⁹ = 6720409 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6720929) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5640 + ... + 6726.

It is an arithmetic number, because the mean of its divisors is an integer number (625600).

Almost surely, 2^6720921 is an apocalyptic number.

It is an amenable number.

6720921 is a deficient number, since it is larger than the sum of its proper divisors (3288679).

6720921 is a wasteful number, since it uses less digits than its factorization.

6720921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1325 (or 1319 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 6720921 is about 2592.4739150086. The cubic root of 6720921 is about 188.7163798430.

The spelling of 6720921 in words is "six million, seven hundred twenty thousand, nine hundred twenty-one".