6420908991 has 48 divisors (see below), whose sum is σ = 10123491840. Its totient is φ = 3608841600.

The previous prime is 6420908987. The next prime is 6420908999. The reversal of 6420908991 is 1998090246.

It is not a de Polignac number, because 6420908991 - 2² = 6420908987 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 6420908991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6420908999) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3564291 + ... + 3566091.

It is an arithmetic number, because the mean of its divisors is an integer number (210906080).

Almost surely, 2^6420908991 is an apocalyptic number.

6420908991 is a deficient number, since it is larger than the sum of its proper divisors (3702582849).

6420908991 is a wasteful number, since it uses less digits than its factorization.

6420908991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2204 (or 2197 counting only the distinct ones).

The product of its (nonzero) digits is 279936, while the sum is 48.

The square root of 6420908991 is about 80130.5746329078. The cubic root of 6420908991 is about 1858.6552301351.

The spelling of 6420908991 in words is "six billion, four hundred twenty million, nine hundred eight thousand, nine hundred ninety-one".