638600821 has 2 divisors, whose sum is σ = 638600822. Its totient is φ = 638600820.

The previous prime is 638600813. The next prime is 638600827. The reversal of 638600821 is 128006836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 394022500 + 244578321 = 19850^2 + 15639^2 .

It is a cyclic number.

It is not a de Polignac number, because 638600821 - 2³ = 638600813 is a prime.

It is a super-2 number, since 2×638600821² = 815622017163748082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638600827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319300410 + 319300411.

It is an arithmetic number, because the mean of its divisors is an integer number (319300411).

Almost surely, 2^638600821 is an apocalyptic number.

It is an amenable number.

638600821 is a deficient number, since it is larger than the sum of its proper divisors (1).

638600821 is an equidigital number, since it uses as much as digits as its factorization.

638600821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 638600821 is about 25270.5524474634. The cubic root of 638600821 is about 861.1454095154.

The spelling of 638600821 in words is "six hundred thirty-eight million, six hundred thousand, eight hundred twenty-one".