6421646391 has 32 divisors (see below), whose sum is σ = 9415802880. Its totient is φ = 3874860000.

The previous prime is 6421646389. The next prime is 6421646393. The reversal of 6421646391 is 1936461246.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (6421646389) and next prime (6421646393).

It is not a de Polignac number, because 6421646391 - 2¹ = 6421646389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6421646393) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1349266 + ... + 1354016.

It is an arithmetic number, because the mean of its divisors is an integer number (294243840).

Almost surely, 2^6421646391 is an apocalyptic number.

6421646391 is a deficient number, since it is larger than the sum of its proper divisors (2994156489).

6421646391 is a wasteful number, since it uses less digits than its factorization.

6421646391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5827.

The product of its digits is 186624, while the sum is 42.

The square root of 6421646391 is about 80135.1757407445. The cubic root of 6421646391 is about 1858.7263789348.

The spelling of 6421646391 in words is "six billion, four hundred twenty-one million, six hundred forty-six thousand, three hundred ninety-one".