642636985 has 4 divisors (see below), whose sum is σ = 771164388. Its totient is φ = 514109584.

The previous prime is 642636983. The next prime is 642636991. The reversal of 642636985 is 589636246.

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

It can be written as a sum of positive squares in 2 ways, for example, as 208831401 + 433805584 = 14451^2 + 20828^2 .

It is a cyclic number.

It is not a de Polignac number, because 642636985 - 2¹ = 642636983 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642636983) 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, 64263694 + ... + 64263703.

It is an arithmetic number, because the mean of its divisors is an integer number (192791097).

Almost surely, 2^642636985 is an apocalyptic number.

It is an amenable number.

642636985 is a deficient number, since it is larger than the sum of its proper divisors (128527403).

642636985 is a wasteful number, since it uses less digits than its factorization.

642636985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128527402.

The product of its digits is 1866240, while the sum is 49.

The square root of 642636985 is about 25350.2856985873. The cubic root of 642636985 is about 862.9558399769.

The spelling of 642636985 in words is "six hundred forty-two million, six hundred thirty-six thousand, nine hundred eighty-five".