638042681 has 2 divisors, whose sum is σ = 638042682. Its totient is φ = 638042680.

The previous prime is 638042641. The next prime is 638042723. The reversal of 638042681 is 186240836.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 638017081 + 25600 = 25259^2 + 160^2 .

It is a cyclic number.

It is not a de Polignac number, because 638042681 - 2¹⁸ = 637780537 is a prime.

It is a super-2 number, since 2×638042681² = 814196925555335522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (638042611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319021340 + 319021341.

It is an arithmetic number, because the mean of its divisors is an integer number (319021341).

Almost surely, 2^638042681 is an apocalyptic number.

It is an amenable number.

638042681 is a deficient number, since it is larger than the sum of its proper divisors (1).

638042681 is an equidigital number, since it uses as much as digits as its factorization.

638042681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 55296, while the sum is 38.

The square root of 638042681 is about 25259.5067449861. The cubic root of 638042681 is about 860.8944547311.

The spelling of 638042681 in words is "six hundred thirty-eight million, forty-two thousand, six hundred eighty-one".