1687638851 has 4 divisors (see below), whose sum is σ = 1688003304. Its totient is φ = 1687274400.

The previous prime is 1687638793. The next prime is 1687638859. The reversal of 1687638851 is 1588367861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1588367861 = 67 ⋅23706983.

It is a cyclic number.

It is not a de Polignac number, because 1687638851 - 2²⁶ = 1620529987 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1687638793 and 1687638802.

It is not an unprimeable number, because it can be changed into a prime (1687638859) 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, 175190 + ... + 184571.

It is an arithmetic number, because the mean of its divisors is an integer number (422000826).

Almost surely, 2^1687638851 is an apocalyptic number.

1687638851 is a deficient number, since it is larger than the sum of its proper divisors (364453).

1687638851 is an equidigital number, since it uses as much as digits as its factorization.

1687638851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364452.

The product of its digits is 1935360, while the sum is 53.

The square root of 1687638851 is about 41080.8818186757. The cubic root of 1687638851 is about 1190.5834417433.

The spelling of 1687638851 in words is "one billion, six hundred eighty-seven million, six hundred thirty-eight thousand, eight hundred fifty-one".