166551561 has 24 divisors (see below), whose sum is σ = 270915840. Its totient is φ = 97682400.

The previous prime is 166551557. The next prime is 166551563. The reversal of 166551561 is 165155661.

It is not a de Polignac number, because 166551561 - 2² = 166551557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166551563) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24066 + ... + 30203.

It is an arithmetic number, because the mean of its divisors is an integer number (11288160).

Almost surely, 2^166551561 is an apocalyptic number.

166551561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

166551561 is a deficient number, since it is larger than the sum of its proper divisors (104364279).

166551561 is a wasteful number, since it uses less digits than its factorization.

166551561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54317 (or 54314 counting only the distinct ones).

The product of its digits is 27000, while the sum is 36.

The square root of 166551561 is about 12905.4856940760. The cubic root of 166551561 is about 550.1944887933.

The spelling of 166551561 in words is "one hundred sixty-six million, five hundred fifty-one thousand, five hundred sixty-one".