6421720628 has 6 divisors (see below), whose sum is σ = 11238011106. Its totient is φ = 3210860312.

The previous prime is 6421720619. The next prime is 6421720633. The reversal of 6421720628 is 8260271246.

It can be written as a sum of positive squares in only one way, i.e., 4331219344 + 2090501284 = 65812^2 + 45722^2 .

It is a junction number, because it is equal to n+sod(n) for n = 6421720591 and 6421720600.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 802715075 + ... + 802715082.

It is an arithmetic number, because the mean of its divisors is an integer number (1873001851).

Almost surely, 2^6421720628 is an apocalyptic number.

It is an amenable number.

6421720628 is a deficient number, since it is larger than the sum of its proper divisors (4816290478).

6421720628 is a wasteful number, since it uses less digits than its factorization.

6421720628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1605430161 (or 1605430159 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 38.

The square root of 6421720628 is about 80135.6389379906. The cubic root of 6421720628 is about 1858.7335414666.

The spelling of 6421720628 in words is "six billion, four hundred twenty-one million, seven hundred twenty thousand, six hundred twenty-eight".