1666878511 has 4 divisors (see below), whose sum is σ = 1670448312. Its totient is φ = 1663308712.

The previous prime is 1666878503. The next prime is 1666878533. The reversal of 1666878511 is 1158786661.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1666878511 - 2³ = 1666878503 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666878541) 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, 1784200 + ... + 1785133.

It is an arithmetic number, because the mean of its divisors is an integer number (417612078).

Almost surely, 2^1666878511 is an apocalyptic number.

1666878511 is a deficient number, since it is larger than the sum of its proper divisors (3569801).

1666878511 is an equidigital number, since it uses as much as digits as its factorization.

1666878511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3569800.

The product of its digits is 483840, while the sum is 49.

The square root of 1666878511 is about 40827.4235165532. The cubic root of 1666878511 is about 1185.6813332145.

The spelling of 1666878511 in words is "one billion, six hundred sixty-six million, eight hundred seventy-eight thousand, five hundred eleven".