6443645991 has 4 divisors (see below), whose sum is σ = 8591527992. Its totient is φ = 4295763992.

The previous prime is 6443645963. The next prime is 6443645993. The reversal of 6443645991 is 1995463446.

6443645991 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6443645991 - 2¹⁵ = 6443613223 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6443645993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1073940996 + ... + 1073941001.

It is an arithmetic number, because the mean of its divisors is an integer number (2147881998).

Almost surely, 2^6443645991 is an apocalyptic number.

6443645991 is a deficient number, since it is larger than the sum of its proper divisors (2147882001).

6443645991 is a wasteful number, since it uses less digits than its factorization.

6443645991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2147882000.

The product of its digits is 2799360, while the sum is 51.

The square root of 6443645991 is about 80272.3239416924. The cubic root of 6443645991 is about 1860.8465325152.

The spelling of 6443645991 in words is "six billion, four hundred forty-three million, six hundred forty-five thousand, nine hundred ninety-one".