6643531 has 4 divisors (see below), whose sum is σ = 6648952. Its totient is φ = 6638112.

The previous prime is 6643513. The next prime is 6643537. The reversal of 6643531 is 1353466.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1353466 = 2 ⋅676733.

It is a cyclic number.

It is not a de Polignac number, because 6643531 - 2⁵ = 6643499 is a prime.

It is a super-2 number, since 2×6643531² = 88273008295922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 6643531.

It is not an unprimeable number, because it can be changed into a prime (6643537) 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, 100 + ... + 3646.

It is an arithmetic number, because the mean of its divisors is an integer number (1662238).

Almost surely, 2^6643531 is an apocalyptic number.

6643531 is a deficient number, since it is larger than the sum of its proper divisors (5421).

6643531 is a wasteful number, since it uses less digits than its factorization.

6643531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5420.

The product of its digits is 6480, while the sum is 28.

The square root of 6643531 is about 2577.5048011594. The cubic root of 6643531 is about 187.9892384816.

Adding to 6643531 its reverse (1353466), we get a palindrome (7996997).

It can be divided in two parts, 66435 and 31, that added together give a palindrome (66466).

The spelling of 6643531 in words is "six million, six hundred forty-three thousand, five hundred thirty-one".