638920739 has 2 divisors, whose sum is σ = 638920740. Its totient is φ = 638920738.

The previous prime is 638920729. The next prime is 638920759. The reversal of 638920739 is 937029836.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 638920739 - 2²⁰ = 637872163 is a prime.

It is a super-2 number, since 2×638920739² = 816439421448612242, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 638920693 and 638920702.

It is not a weakly prime, because it can be changed into another prime (638920729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319460369 + 319460370.

It is an arithmetic number, because the mean of its divisors is an integer number (319460370).

Almost surely, 2^638920739 is an apocalyptic number.

638920739 is a deficient number, since it is larger than the sum of its proper divisors (1).

638920739 is an equidigital number, since it uses as much as digits as its factorization.

638920739 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 489888, while the sum is 47.

The square root of 638920739 is about 25276.8815125600. The cubic root of 638920739 is about 861.2891873477.

The spelling of 638920739 in words is "six hundred thirty-eight million, nine hundred twenty thousand, seven hundred thirty-nine".