1666557457 has 2 divisors, whose sum is σ = 1666557458. Its totient is φ = 1666557456.

The previous prime is 1666557439. The next prime is 1666557479. The reversal of 1666557457 is 7547556661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 836887041 + 829670416 = 28929^2 + 28804^2 .

It is an emirp because it is prime and its reverse (7547556661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666557457 - 2¹¹ = 1666555409 is a prime.

It is not a weakly prime, because it can be changed into another prime (1666257457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833278728 + 833278729.

It is an arithmetic number, because the mean of its divisors is an integer number (833278729).

Almost surely, 2^1666557457 is an apocalyptic number.

It is an amenable number.

1666557457 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666557457 is an equidigital number, since it uses as much as digits as its factorization.

1666557457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5292000, while the sum is 52.

The square root of 1666557457 is about 40823.4914846832. The cubic root of 1666557457 is about 1185.6052044556.

The spelling of 1666557457 in words is "one billion, six hundred sixty-six million, five hundred fifty-seven thousand, four hundred fifty-seven".