1688653640221 has 4 divisors (see below), whose sum is σ = 1716336486844. Its totient is φ = 1660970793600.

The previous prime is 1688653640203. The next prime is 1688653640251. The reversal of 1688653640221 is 1220463568861.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 370430476900 + 1318223163321 = 608630^2 + 1148139^2 .

It is a cyclic number.

It is not a de Polignac number, because 1688653640221 - 2⁹ = 1688653639709 is a prime.

It is a super-2 number, since 2×1688653640221² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1688653640251) 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, 13841423220 + ... + 13841423341.

It is an arithmetic number, because the mean of its divisors is an integer number (429084121711).

Almost surely, 2^{1688653640221} is an apocalyptic number.

It is an amenable number.

1688653640221 is a deficient number, since it is larger than the sum of its proper divisors (27682846623).

1688653640221 is an equidigital number, since it uses as much as digits as its factorization.

1688653640221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27682846622.

The product of its (nonzero) digits is 3317760, while the sum is 52.

The spelling of 1688653640221 in words is "one trillion, six hundred eighty-eight billion, six hundred fifty-three million, six hundred forty thousand, two hundred twenty-one".