121691905 has 4 divisors (see below), whose sum is σ = 146030292. Its totient is φ = 97353520.

The previous prime is 121691891. The next prime is 121691909. The reversal of 121691905 is 509196121.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 87011584 + 34680321 = 9328^2 + 5889^2 .

It is not a de Polignac number, because 121691905 - 2⁹ = 121691393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121691909) 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, 12169186 + ... + 12169195.

It is an arithmetic number, because the mean of its divisors is an integer number (36507573).

Almost surely, 2^121691905 is an apocalyptic number.

It is an amenable number.

121691905 is a deficient number, since it is larger than the sum of its proper divisors (24338387).

121691905 is an equidigital number, since it uses as much as digits as its factorization.

121691905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24338386.

The product of its (nonzero) digits is 4860, while the sum is 34.

The square root of 121691905 is about 11031.4053955061. The cubic root of 121691905 is about 495.5497140949.

The spelling of 121691905 in words is "one hundred twenty-one million, six hundred ninety-one thousand, nine hundred five".