638428581 has 32 divisors (see below), whose sum is σ = 1095768320. Its totient is φ = 359811072.

The previous prime is 638428577. The next prime is 638428603. The reversal of 638428581 is 185824836.

638428581 is a `hidden beast` number, since 63 + 8 + 4 + 2 + 8 + 581 = 666.

It is not a de Polignac number, because 638428581 - 2² = 638428577 is a prime.

It is a super-3 number, since 3×638428581³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638428561) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9340 + ... + 36933.

It is an arithmetic number, because the mean of its divisors is an integer number (34242760).

Almost surely, 2^638428581 is an apocalyptic number.

It is an amenable number.

638428581 is a deficient number, since it is larger than the sum of its proper divisors (457339739).

638428581 is a wasteful number, since it uses less digits than its factorization.

638428581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46362 (or 46356 counting only the distinct ones).

The product of its digits is 368640, while the sum is 45.

The square root of 638428581 is about 25267.1442984758. The cubic root of 638428581 is about 861.0679813749.

The spelling of 638428581 in words is "six hundred thirty-eight million, four hundred twenty-eight thousand, five hundred eighty-one".