121688647921 has 3 divisors (see below), whose sum is σ = 121688996761. Its totient is φ = 121688299082.

The previous prime is 121688647907. The next prime is 121688647933. The reversal of 121688647921 is 129746886121.

The square root of 121688647921 is 348839.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 121688647921 - 2²⁵ = 121655093489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121688647991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 174420 + ... + 523258.

Almost surely, 2^121688647921 is an apocalyptic number.

121688647921 is the 348839-th square number.

121688647921 is the 174420-th centered octagonal number.

It is an amenable number.

121688647921 is a deficient number, since it is larger than the sum of its proper divisors (348840).

121688647921 is an frugal number, since it uses more digits than its factorization.

121688647921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 697678 (or 348839 counting only the distinct ones).

The product of its digits is 2322432, while the sum is 55.

The spelling of 121688647921 in words is "one hundred twenty-one billion, six hundred eighty-eight million, six hundred forty-seven thousand, nine hundred twenty-one".