1666137601 has 4 divisors (see below), whose sum is σ = 1686211632. Its totient is φ = 1646063572.

The previous prime is 1666137559. The next prime is 1666137611. The reversal of 1666137601 is 1067316661.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1067316661 = 17 ⋅62783333.

It is a cyclic number.

It is not a de Polignac number, because 1666137601 - 2²¹ = 1664040449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666137611) 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, 10036891 + ... + 10037056.

It is an arithmetic number, because the mean of its divisors is an integer number (421552908).

Almost surely, 2^1666137601 is an apocalyptic number.

It is an amenable number.

1666137601 is a deficient number, since it is larger than the sum of its proper divisors (20074031).

1666137601 is an equidigital number, since it uses as much as digits as its factorization.

1666137601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20074030.

The product of its (nonzero) digits is 27216, while the sum is 37.

The square root of 1666137601 is about 40818.3488274575. The cubic root of 1666137601 is about 1185.5056328777.

The spelling of 1666137601 in words is "one billion, six hundred sixty-six million, one hundred thirty-seven thousand, six hundred one".