1666720511 has 8 divisors (see below), whose sum is σ = 1770874560. Its totient is φ = 1568673504.

The previous prime is 1666720493. The next prime is 1666720519. The reversal of 1666720511 is 1150276661.

It is not a de Polignac number, because 1666720511 - 2²⁶ = 1599611647 is a prime.

It is a super-2 number, since 2×1666720511² = 5555914523576202242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666720519) 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 7 ways as a sum of consecutive naturals, for example, 164711 + ... + 174536.

It is an arithmetic number, because the mean of its divisors is an integer number (221359320).

Almost surely, 2^1666720511 is an apocalyptic number.

1666720511 is a deficient number, since it is larger than the sum of its proper divisors (104154049).

1666720511 is an frugal number, since it uses more digits than its factorization.

1666720511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339298 (or 339264 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 1666720511 is about 40825.4884967712. The cubic root of 1666720511 is about 1185.6438692624.

The spelling of 1666720511 in words is "one billion, six hundred sixty-six million, seven hundred twenty thousand, five hundred eleven".