166665551 has 4 divisors (see below), whose sum is σ = 179485992. Its totient is φ = 153845112.

The previous prime is 166665539. The next prime is 166665557. The reversal of 166665551 is 155566661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155566661 = 19 ⋅8187719.

It is a cyclic number.

It is not a de Polignac number, because 166665551 - 2⁶ = 166665487 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 166665499 and 166665508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166665557) 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, 6410201 + ... + 6410226.

It is an arithmetic number, because the mean of its divisors is an integer number (44871498).

Almost surely, 2^166665551 is an apocalyptic number.

166665551 is a deficient number, since it is larger than the sum of its proper divisors (12820441).

166665551 is a wasteful number, since it uses less digits than its factorization.

166665551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12820440.

The product of its digits is 162000, while the sum is 41.

The square root of 166665551 is about 12909.9012777015. The cubic root of 166665551 is about 550.3199801963.

The spelling of 166665551 in words is "one hundred sixty-six million, six hundred sixty-five thousand, five hundred fifty-one".