1685542217821 has 8 divisors (see below), whose sum is σ = 2101455232704. Its totient is φ = 1313409520320.

The previous prime is 1685542217741. The next prime is 1685542217873. The reversal of 1685542217821 is 1287122455861.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1685542217821 - 2²⁵ = 1685508663389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1685542217881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10945079260 + ... + 10945079413.

It is an arithmetic number, because the mean of its divisors is an integer number (262681904088).

Almost surely, 2^{1685542217821} is an apocalyptic number.

1685542217821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1685542217821 is a deficient number, since it is larger than the sum of its proper divisors (415913014883).

1685542217821 is a wasteful number, since it uses less digits than its factorization.

1685542217821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21890158691.

The product of its digits is 2150400, while the sum is 52.

The spelling of 1685542217821 in words is "one trillion, six hundred eighty-five billion, five hundred forty-two million, two hundred seventeen thousand, eight hundred twenty-one".