1666740401721 has 6 divisors (see below), whose sum is σ = 2407513913610. Its totient is φ = 1111160267808.

The previous prime is 1666740401693. The next prime is 1666740401813. The reversal of 1666740401721 is 1271040476661.

It can be written as a sum of positive squares in only one way, i.e., 1553163987600 + 113576414121 = 1246260^2 + 337011^2 .

It is not a de Polignac number, because 1666740401721 - 2¹³ = 1666740393529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1666740408721) 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 5 ways as a sum of consecutive naturals, for example, 92596688976 + ... + 92596688993.

It is an arithmetic number, because the mean of its divisors is an integer number (401252318935).

Almost surely, 2^{1666740401721} is an apocalyptic number.

It is an amenable number.

1666740401721 is a deficient number, since it is larger than the sum of its proper divisors (740773511889).

1666740401721 is a wasteful number, since it uses less digits than its factorization.

1666740401721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185193377975 (or 185193377972 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 45.

The spelling of 1666740401721 in words is "one trillion, six hundred sixty-six billion, seven hundred forty million, four hundred one thousand, seven hundred twenty-one".