121691 has 4 divisors (see below), whose sum is σ = 123432. Its totient is φ = 119952.

The previous prime is 121687. The next prime is 121697. The reversal of 121691 is 196121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196121 = 23 ⋅8527.

It is a cyclic number.

It is not a de Polignac number, because 121691 - 2² = 121687 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 (121697) 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, 761 + ... + 906.

It is an arithmetic number, because the mean of its divisors is an integer number (30858).

2¹²¹⁶⁹¹ is an apocalyptic number.

121691 is a deficient number, since it is larger than the sum of its proper divisors (1741).

121691 is an equidigital number, since it uses as much as digits as its factorization.

121691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1740.

The product of its digits is 108, while the sum is 20.

The square root of 121691 is about 348.8423712796. The cubic root of 121691 is about 49.5548485655.

The spelling of 121691 in words is "one hundred twenty-one thousand, six hundred ninety-one".