1666843509257 has 4 divisors (see below), whose sum is σ = 1666870461456. Its totient is φ = 1666816557060.

The previous prime is 1666843509251. The next prime is 1666843509313. The reversal of 1666843509257 is 7529053486661.

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 1666843509257 - 2⁴ = 1666843509241 is a prime.

It is a super-3 number, since 3×1666843509257³ (a number of 38 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1666843509257.

It is not an unprimeable number, because it can be changed into a prime (1666843509251) 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, 13383119 + ... + 13507092.

It is an arithmetic number, because the mean of its divisors is an integer number (416717615364).

It is a 1-persistent number, because it is pandigital, but 2⋅1666843509257 = 3333687018514 is not.

Almost surely, 2^{1666843509257} is an apocalyptic number.

It is an amenable number.

1666843509257 is a deficient number, since it is larger than the sum of its proper divisors (26952199).

1666843509257 is an equidigital number, since it uses as much as digits as its factorization.

1666843509257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26952198.

The product of its (nonzero) digits is 65318400, while the sum is 62.

The spelling of 1666843509257 in words is "one trillion, six hundred sixty-six billion, eight hundred forty-three million, five hundred nine thousand, two hundred fifty-seven".