1638138091 has 2 divisors, whose sum is σ = 1638138092. Its totient is φ = 1638138090.

The previous prime is 1638138083. The next prime is 1638138097. The reversal of 1638138091 is 1908318361.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1638138091 - 2³ = 1638138083 is a prime.

It is not a weakly prime, because it can be changed into another prime (1638138097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819069045 + 819069046.

It is an arithmetic number, because the mean of its divisors is an integer number (819069046).

Almost surely, 2^1638138091 is an apocalyptic number.

1638138091 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638138091 is an equidigital number, since it uses as much as digits as its factorization.

1638138091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 1638138091 is about 40473.9186513982. The cubic root of 1638138091 is about 1178.8272584435.

The spelling of 1638138091 in words is "one billion, six hundred thirty-eight million, one hundred thirty-eight thousand, ninety-one".