170121991 has 12 divisors (see below), whose sum is σ = 193914120. Its totient is φ = 148767840.

The previous prime is 170121977. The next prime is 170122049. The reversal of 170121991 is 199121071.

It is a happy number.

170121991 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 170121991 - 2²¹ = 168024839 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 (170121191) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 23280 + ... + 29701.

It is an arithmetic number, because the mean of its divisors is an integer number (16159510).

Almost surely, 2^170121991 is an apocalyptic number.

170121991 is a deficient number, since it is larger than the sum of its proper divisors (23792129).

170121991 is a wasteful number, since it uses less digits than its factorization.

170121991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53026 (or 53013 counting only the distinct ones).

The product of its (nonzero) digits is 1134, while the sum is 31.

The square root of 170121991 is about 13043.0821127523. The cubic root of 170121991 is about 554.0983015318.

The spelling of 170121991 in words is "one hundred seventy million, one hundred twenty-one thousand, nine hundred ninety-one".