168991221 has 16 divisors (see below), whose sum is σ = 258121728. Its totient is φ = 96337200.

The previous prime is 168991213. The next prime is 168991241. The reversal of 168991221 is 122199861.

168991221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 168991221 - 2³ = 168991213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 168991221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (168991241) 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, 285 + ... + 18386.

It is an arithmetic number, because the mean of its divisors is an integer number (16132608).

Almost surely, 2^168991221 is an apocalyptic number.

It is an amenable number.

168991221 is a deficient number, since it is larger than the sum of its proper divisors (89130507).

168991221 is a wasteful number, since it uses less digits than its factorization.

168991221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19112.

The product of its digits is 15552, while the sum is 39.

The square root of 168991221 is about 12999.6623417687. The cubic root of 168991221 is about 552.8679078068.

The spelling of 168991221 in words is "one hundred sixty-eight million, nine hundred ninety-one thousand, two hundred twenty-one".