1638125257 has 4 divisors (see below), whose sum is σ = 1642688640. Its totient is φ = 1633561876.

The previous prime is 1638125239. The next prime is 1638125273. The reversal of 1638125257 is 7525218361.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1638125257 - 2⁷ = 1638125129 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1638125207) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2281153 + ... + 2281870.

It is an arithmetic number, because the mean of its divisors is an integer number (410672160).

Almost surely, 2^1638125257 is an apocalyptic number.

It is an amenable number.

1638125257 is a deficient number, since it is larger than the sum of its proper divisors (4563383).

1638125257 is an equidigital number, since it uses as much as digits as its factorization.

1638125257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4563382.

The product of its digits is 100800, while the sum is 40.

The square root of 1638125257 is about 40473.7601045418. The cubic root of 1638125257 is about 1178.8241799264.

The spelling of 1638125257 in words is "one billion, six hundred thirty-eight million, one hundred twenty-five thousand, two hundred fifty-seven".