638433281 has 4 divisors (see below), whose sum is σ = 641173572. Its totient is φ = 635692992.

The previous prime is 638433239. The next prime is 638433293. The reversal of 638433281 is 182334836.

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 57623281 + 580810000 = 7591^2 + 24100^2 .

It is a cyclic number.

It is not a de Polignac number, because 638433281 - 2⁶ = 638433217 is a prime.

It is a super-2 number, since 2×638433281² = 815194108576849922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638423281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1369796 + ... + 1370261.

It is an arithmetic number, because the mean of its divisors is an integer number (160293393).

Almost surely, 2^638433281 is an apocalyptic number.

It is an amenable number.

638433281 is a deficient number, since it is larger than the sum of its proper divisors (2740291).

638433281 is a wasteful number, since it uses less digits than its factorization.

638433281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2740290.

The product of its digits is 82944, while the sum is 38.

The square root of 638433281 is about 25267.2373044621. The cubic root of 638433281 is about 861.0700943805.

The spelling of 638433281 in words is "six hundred thirty-eight million, four hundred thirty-three thousand, two hundred eighty-one".