1638377813 has 2 divisors, whose sum is σ = 1638377814. Its totient is φ = 1638377812.

The previous prime is 1638377803. The next prime is 1638377857. The reversal of 1638377813 is 3187738361.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1480171729 + 158206084 = 38473^2 + 12578^2 .

It is a cyclic number.

It is not a de Polignac number, because 1638377813 - 2⁶ = 1638377749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1638377803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819188906 + 819188907.

It is an arithmetic number, because the mean of its divisors is an integer number (819188907).

Almost surely, 2^1638377813 is an apocalyptic number.

It is an amenable number.

1638377813 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638377813 is an equidigital number, since it uses as much as digits as its factorization.

1638377813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 508032, while the sum is 47.

The square root of 1638377813 is about 40476.8799810460. The cubic root of 1638377813 is about 1178.8847580821.

The spelling of 1638377813 in words is "one billion, six hundred thirty-eight million, three hundred seventy-seven thousand, eight hundred thirteen".