638301991 has 2 divisors, whose sum is σ = 638301992. Its totient is φ = 638301990.

The previous prime is 638301967. The next prime is 638302051. The reversal of 638301991 is 199103836.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 638301991 - 2⁵ = 638301959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638301901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319150995 + 319150996.

It is an arithmetic number, because the mean of its divisors is an integer number (319150996).

Almost surely, 2^638301991 is an apocalyptic number.

638301991 is a deficient number, since it is larger than the sum of its proper divisors (1).

638301991 is an equidigital number, since it uses as much as digits as its factorization.

638301991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34992, while the sum is 40.

The square root of 638301991 is about 25264.6391424853. The cubic root of 638301991 is about 861.0110656894.

The spelling of 638301991 in words is "six hundred thirty-eight million, three hundred one thousand, nine hundred ninety-one".