1638489857 has 2 divisors, whose sum is σ = 1638489858. Its totient is φ = 1638489856.

The previous prime is 1638489799. The next prime is 1638489877. The reversal of 1638489857 is 7589848361.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1138117696 + 500372161 = 33736^2 + 22369^2 .

It is a cyclic number.

It is not a de Polignac number, because 1638489857 - 2⁶ = 1638489793 is a prime.

It is a super-2 number, since 2×1638489857² = 5369298022983760898, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1638489796 and 1638489805.

It is not a weakly prime, because it can be changed into another prime (1638489877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819244928 + 819244929.

It is an arithmetic number, because the mean of its divisors is an integer number (819244929).

Almost surely, 2^1638489857 is an apocalyptic number.

It is an amenable number.

1638489857 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638489857 is an equidigital number, since it uses as much as digits as its factorization.

1638489857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11612160, while the sum is 59.

The square root of 1638489857 is about 40478.2640067481. The cubic root of 1638489857 is about 1178.9116309950.

The spelling of 1638489857 in words is "one billion, six hundred thirty-eight million, four hundred eighty-nine thousand, eight hundred fifty-seven".