638865421 has 8 divisors (see below), whose sum is σ = 659436800. Its totient is φ = 618468048.

The previous prime is 638865419. The next prime is 638865433. The reversal of 638865421 is 124568836.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638865421 - 2¹ = 638865419 is a prime.

It is a super-2 number, since 2×638865421² = 816298052299014482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638860421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36021 + ... + 50746.

It is an arithmetic number, because the mean of its divisors is an integer number (82429600).

Almost surely, 2^638865421 is an apocalyptic number.

It is an amenable number.

638865421 is a deficient number, since it is larger than the sum of its proper divisors (20571379).

638865421 is a wasteful number, since it uses less digits than its factorization.

638865421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87003.

The product of its digits is 276480, while the sum is 43.

The square root of 638865421 is about 25275.7872478782. The cubic root of 638865421 is about 861.2643297154.

The spelling of 638865421 in words is "six hundred thirty-eight million, eight hundred sixty-five thousand, four hundred twenty-one".