1638619891109 has 2 divisors, whose sum is σ = 1638619891110. Its totient is φ = 1638619891108.

The previous prime is 1638619891099. The next prime is 1638619891127. The reversal of 1638619891109 is 9011989168361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1638599686084 + 20205025 = 1280078^2 + 4495^2 .

It is an emirp because it is prime and its reverse (9011989168361) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1638619891109 - 2¹⁶ = 1638619825573 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1638619191109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819309945554 + 819309945555.

It is an arithmetic number, because the mean of its divisors is an integer number (819309945555).

Almost surely, 2^{1638619891109} is an apocalyptic number.

It is an amenable number.

1638619891109 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638619891109 is an equidigital number, since it uses as much as digits as its factorization.

1638619891109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5038848, while the sum is 62.

The spelling of 1638619891109 in words is "one trillion, six hundred thirty-eight billion, six hundred nineteen million, eight hundred ninety-one thousand, one hundred nine".