166661639 has 4 divisors (see below), whose sum is σ = 168771360. Its totient is φ = 164551920.

The previous prime is 166661609. The next prime is 166661681. The reversal of 166661639 is 936166661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 936166661 = 29 ⋅32281609.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-166661639 is a prime.

It is a super-2 number, since 2×166661639² = 55552203828332642, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 166661639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166661609) 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, 1054742 + ... + 1054899.

It is an arithmetic number, because the mean of its divisors is an integer number (42192840).

Almost surely, 2^166661639 is an apocalyptic number.

166661639 is a deficient number, since it is larger than the sum of its proper divisors (2109721).

166661639 is an equidigital number, since it uses as much as digits as its factorization.

166661639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2109720.

The product of its digits is 209952, while the sum is 44.

The square root of 166661639 is about 12909.7497651968. The cubic root of 166661639 is about 550.3156744303.

The spelling of 166661639 in words is "one hundred sixty-six million, six hundred sixty-one thousand, six hundred thirty-nine".