166101991 has 16 divisors (see below), whose sum is σ = 190447488. Its totient is φ = 143488800.

The previous prime is 166101989. The next prime is 166101997. The reversal of 166101991 is 199101661.

It is a cyclic number.

It is not a de Polignac number, because 166101991 - 2¹ = 166101989 is a prime.

166101991 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166101997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12756 + ... + 22246.

It is an arithmetic number, because the mean of its divisors is an integer number (11902968).

Almost surely, 2^166101991 is an apocalyptic number.

166101991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

166101991 is a deficient number, since it is larger than the sum of its proper divisors (24345497).

166101991 is a wasteful number, since it uses less digits than its factorization.

166101991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9582.

The product of its (nonzero) digits is 2916, while the sum is 34.

The square root of 166101991 is about 12888.0561373700. The cubic root of 166101991 is about 549.6989989362.

The spelling of 166101991 in words is "one hundred sixty-six million, one hundred one thousand, nine hundred ninety-one".