6721820 has 72 divisors (see below), whose sum is σ = 17332560. Its totient is φ = 2183328.

The previous prime is 6721789. The next prime is 6721843. The reversal of 6721820 is 281276.

It is a super-2 number, since 2×6721820² = 90365728224800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 6721820.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 353771 + ... + 353789.

It is an arithmetic number, because the mean of its divisors is an integer number (240730).

Almost surely, 2^6721820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6721820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8666280).

6721820 is an abundant number, since it is smaller than the sum of its proper divisors (10610740).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6721820 is a wasteful number, since it uses less digits than its factorization.

6721820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80 (or 33 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 6721820 is about 2592.6472957192. The cubic root of 6721820 is about 188.7247937921.

The spelling of 6721820 in words is "six million, seven hundred twenty-one thousand, eight hundred twenty".