636664643 has 4 divisors (see below), whose sum is σ = 636739080. Its totient is φ = 636590208.

The previous prime is 636664631. The next prime is 636664649. The reversal of 636664643 is 346466636.

It is a happy number.

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 636664643 - 2¹⁶ = 636599107 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 636664594 and 636664603.

It is not an unprimeable number, because it can be changed into a prime (636664649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22430 + ... + 42147.

It is an arithmetic number, because the mean of its divisors is an integer number (159184770).

Almost surely, 2^636664643 is an apocalyptic number.

636664643 is a deficient number, since it is larger than the sum of its proper divisors (74437).

636664643 is an equidigital number, since it uses as much as digits as its factorization.

636664643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74436.

The product of its digits is 1119744, while the sum is 44.

The square root of 636664643 is about 25232.2143895458. The cubic root of 636664643 is about 860.2742243402.

The spelling of 636664643 in words is "six hundred thirty-six million, six hundred sixty-four thousand, six hundred forty-three".