12121921 has 4 divisors (see below), whose sum is σ = 13853632. Its totient is φ = 10390212.

The previous prime is 12121883. The next prime is 12121927. The reversal of 12121921 is 12912121.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12912121 = 443 ⋅29147.

It is not a de Polignac number, because 12121921 - 2⁷ = 12121793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12121927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 865845 + ... + 865858.

It is an arithmetic number, because the mean of its divisors is an integer number (3463408).

Almost surely, 2^12121921 is an apocalyptic number.

It is an amenable number.

12121921 is a deficient number, since it is larger than the sum of its proper divisors (1731711).

12121921 is an equidigital number, since it uses as much as digits as its factorization.

12121921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1731710.

The product of its digits is 72, while the sum is 19.

The square root of 12121921 is about 3481.6549225907. The cubic root of 12121921 is about 229.7155968004.

The spelling of 12121921 in words is "twelve million, one hundred twenty-one thousand, nine hundred twenty-one".