1666991097 has 20 divisors (see below), whose sum is σ = 2492989620. Its totient is φ = 1110081024.

The previous prime is 1666991089. The next prime is 1666991101. The reversal of 1666991097 is 7901996661.

It can be written as a sum of positive squares in 2 ways, for example, as 58660281 + 1608330816 = 7659^2 + 40104^2 .

It is not a de Polignac number, because 1666991097 - 2³ = 1666991089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1666991017) 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 19 ways as a sum of consecutive naturals, for example, 64173 + ... + 86325.

It is an arithmetic number, because the mean of its divisors is an integer number (124649481).

Almost surely, 2^1666991097 is an apocalyptic number.

It is an amenable number.

1666991097 is a deficient number, since it is larger than the sum of its proper divisors (825998523).

1666991097 is an equidigital number, since it uses as much as digits as its factorization.

1666991097 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23094 (or 23085 counting only the distinct ones).

The product of its (nonzero) digits is 1102248, while the sum is 54.

The square root of 1666991097 is about 40828.8022969080. The cubic root of 1666991097 is about 1185.7080274442.

The spelling of 1666991097 in words is "one billion, six hundred sixty-six million, nine hundred ninety-one thousand, ninety-seven".