638784649 has 2 divisors, whose sum is σ = 638784650. Its totient is φ = 638784648.

The previous prime is 638784637. The next prime is 638784659. The reversal of 638784649 is 946487836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 571544649 + 67240000 = 23907^2 + 8200^2 .

It is a cyclic number.

It is not a de Polignac number, because 638784649 - 2⁷ = 638784521 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638784649.

It is not a weakly prime, because it can be changed into another prime (638784659) 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, 319392324 + 319392325.

It is an arithmetic number, because the mean of its divisors is an integer number (319392325).

Almost surely, 2^638784649 is an apocalyptic number.

It is an amenable number.

638784649 is a deficient number, since it is larger than the sum of its proper divisors (1).

638784649 is an equidigital number, since it uses as much as digits as its factorization.

638784649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6967296, while the sum is 55.

The square root of 638784649 is about 25274.1893836380. The cubic root of 638784649 is about 861.2280315259.

The spelling of 638784649 in words is "six hundred thirty-eight million, seven hundred eighty-four thousand, six hundred forty-nine".