6403994991 has 24 divisors (see below), whose sum is σ = 9350241264. Its totient is φ = 4223241600.

The previous prime is 6403994963. The next prime is 6403995029. The reversal of 6403994991 is 1994993046.

6403994991 is a `hidden beast` number, since 64 + 0 + 3 + 99 + 499 + 1 = 666.

It is not a de Polignac number, because 6403994991 - 2¹⁷ = 6403863919 is a prime.

It is a super-2 number, since 2×6403994991² = 82022303689506180162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6403994951) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1294675 + ... + 1299611.

It is an arithmetic number, because the mean of its divisors is an integer number (389593386).

Almost surely, 2^6403994991 is an apocalyptic number.

6403994991 is a deficient number, since it is larger than the sum of its proper divisors (2946246273).

6403994991 is a wasteful number, since it uses less digits than its factorization.

6403994991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6471 (or 6468 counting only the distinct ones).

The product of its (nonzero) digits is 1889568, while the sum is 54.

The square root of 6403994991 is about 80024.9647984927. The cubic root of 6403994991 is about 1857.0217677919.

The spelling of 6403994991 in words is "six billion, four hundred three million, nine hundred ninety-four thousand, nine hundred ninety-one".