639686441 has 2 divisors, whose sum is σ = 639686442. Its totient is φ = 639686440.

The previous prime is 639686423. The next prime is 639686459. The reversal of 639686441 is 144686936.

It is a balanced prime because it is at equal distance from previous prime (639686423) and next prime (639686459).

It can be written as a sum of positive squares in only one way, i.e., 639331225 + 355216 = 25285^2 + 596^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639686441 is a prime.

It is a super-4 number, since 4×639686441⁴ (a number of 36 digits) contains 4444 as substring.

It is not a weakly prime, because it can be changed into another prime (639686401) 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, 319843220 + 319843221.

It is an arithmetic number, because the mean of its divisors is an integer number (319843221).

Almost surely, 2^639686441 is an apocalyptic number.

It is an amenable number.

639686441 is a deficient number, since it is larger than the sum of its proper divisors (1).

639686441 is an equidigital number, since it uses as much as digits as its factorization.

639686441 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 746496, while the sum is 47.

The square root of 639686441 is about 25292.0232682164. The cubic root of 639686441 is about 861.6331150250.

The spelling of 639686441 in words is "six hundred thirty-nine million, six hundred eighty-six thousand, four hundred forty-one".