1638671749 has 32 divisors (see below), whose sum is σ = 1995291648. Its totient is φ = 1325376000.

The previous prime is 1638671737. The next prime is 1638671761. The reversal of 1638671749 is 9471768361.

It is an interprime number because it is at equal distance from previous prime (1638671737) and next prime (1638671761).

It is not a de Polignac number, because 1638671749 - 2¹⁹ = 1638147461 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1638671696 and 1638671705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638671719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1386939 + ... + 1388119.

It is an arithmetic number, because the mean of its divisors is an integer number (62352864).

Almost surely, 2^1638671749 is an apocalyptic number.

It is an amenable number.

1638671749 is a deficient number, since it is larger than the sum of its proper divisors (356619899).

1638671749 is a wasteful number, since it uses less digits than its factorization.

1638671749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1549.

The product of its digits is 1524096, while the sum is 52.

The square root of 1638671749 is about 40480.5107304737. The cubic root of 1638671749 is about 1178.9552538182.

The spelling of 1638671749 in words is "one billion, six hundred thirty-eight million, six hundred seventy-one thousand, seven hundred forty-nine".