1638780385 has 16 divisors (see below), whose sum is σ = 2146237632. Its totient is φ = 1191326400.

The previous prime is 1638780347. The next prime is 1638780389. The reversal of 1638780385 is 5830878361.

It is a de Polignac number, because none of the positive numbers 2^k-1638780385 is a prime.

It is a super-3 number, since 3×1638780385³ (a number of 29 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (1638780389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 162130 + ... + 171940.

It is an arithmetic number, because the mean of its divisors is an integer number (134139852).

Almost surely, 2^1638780385 is an apocalyptic number.

It is an amenable number.

1638780385 is a deficient number, since it is larger than the sum of its proper divisors (507457247).

1638780385 is a wasteful number, since it uses less digits than its factorization.

1638780385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12864.

The product of its (nonzero) digits is 967680, while the sum is 49.

The square root of 1638780385 is about 40481.8525391317. The cubic root of 1638780385 is about 1178.9813062502.

The spelling of 1638780385 in words is "one billion, six hundred thirty-eight million, seven hundred eighty thousand, three hundred eighty-five".