638632993 has 4 divisors (see below), whose sum is σ = 640673668. Its totient is φ = 636592320.

The previous prime is 638632963. The next prime is 638633011. The reversal of 638632993 is 399236836.

It is a happy number.

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 78269409 + 560363584 = 8847^2 + 23672^2 .

It is a cyclic number.

It is not a de Polignac number, because 638632993 - 2²¹ = 636535841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638632903) 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, 1019868 + ... + 1020493.

It is an arithmetic number, because the mean of its divisors is an integer number (160168417).

Almost surely, 2^638632993 is an apocalyptic number.

It is an amenable number.

638632993 is a deficient number, since it is larger than the sum of its proper divisors (2040675).

638632993 is a wasteful number, since it uses less digits than its factorization.

638632993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2040674.

The product of its digits is 1259712, while the sum is 49.

The square root of 638632993 is about 25271.1889906273. The cubic root of 638632993 is about 861.1598704556.

The spelling of 638632993 in words is "six hundred thirty-eight million, six hundred thirty-two thousand, nine hundred ninety-three".