1666397571 has 4 divisors (see below), whose sum is σ = 2221863432. Its totient is φ = 1110931712.

The previous prime is 1666397561. The next prime is 1666397581. The reversal of 1666397571 is 1757936661.

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

It is an interprime number because it is at equal distance from previous prime (1666397561) and next prime (1666397581).

It is a cyclic number.

It is not a de Polignac number, because 1666397571 - 2²⁶ = 1599288707 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1666397521) 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, 277732926 + ... + 277732931.

It is an arithmetic number, because the mean of its divisors is an integer number (555465858).

Almost surely, 2^1666397571 is an apocalyptic number.

1666397571 is a deficient number, since it is larger than the sum of its proper divisors (555465861).

1666397571 is an equidigital number, since it uses as much as digits as its factorization.

1666397571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 555465860.

The product of its digits is 1428840, while the sum is 51.

The square root of 1666397571 is about 40821.5331779687. The cubic root of 1666397571 is about 1185.5672884239.

The spelling of 1666397571 in words is "one billion, six hundred sixty-six million, three hundred ninety-seven thousand, five hundred seventy-one".