6721820399 has 16 divisors (see below), whose sum is σ = 8283636480. Its totient is φ = 5325186240.

The previous prime is 6721820333. The next prime is 6721820423. The reversal of 6721820399 is 9930281276.

It is a happy number.

It is not a de Polignac number, because 6721820399 - 2¹⁶ = 6721754863 is a prime.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6721820309) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 610889 + ... + 621794.

It is an arithmetic number, because the mean of its divisors is an integer number (517727280).

Almost surely, 2^6721820399 is an apocalyptic number.

6721820399 is a deficient number, since it is larger than the sum of its proper divisors (1561816081).

6721820399 is a wasteful number, since it uses less digits than its factorization.

6721820399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1232750.

The product of its (nonzero) digits is 326592, while the sum is 47.

The square root of 6721820399 is about 81986.7086728087. The cubic root of 6721820399 is about 1887.2479752623.

The spelling of 6721820399 in words is "six billion, seven hundred twenty-one million, eight hundred twenty thousand, three hundred ninety-nine".