169981661 has 4 divisors (see below), whose sum is σ = 177372192. Its totient is φ = 162591132.

The previous prime is 169981639. The next prime is 169981667. The reversal of 169981661 is 166189961.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-169981661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (169981667) 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, 3695231 + ... + 3695276.

It is an arithmetic number, because the mean of its divisors is an integer number (44343048).

Almost surely, 2^169981661 is an apocalyptic number.

It is an amenable number.

169981661 is a deficient number, since it is larger than the sum of its proper divisors (7390531).

169981661 is an equidigital number, since it uses as much as digits as its factorization.

169981661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7390530.

The product of its digits is 139968, while the sum is 47.

The square root of 169981661 is about 13037.7015228912. The cubic root of 169981661 is about 553.9459049997.

The spelling of 169981661 in words is "one hundred sixty-nine million, nine hundred eighty-one thousand, six hundred sixty-one".