121720643 has 4 divisors (see below), whose sum is σ = 132786168. Its totient is φ = 110655120.

The previous prime is 121720637. The next prime is 121720657. The reversal of 121720643 is 346027121.

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

It is a cyclic number.

It is not a de Polignac number, because 121720643 - 2¹² = 121716547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121720603) 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, 5532746 + ... + 5532767.

It is an arithmetic number, because the mean of its divisors is an integer number (33196542).

Almost surely, 2^121720643 is an apocalyptic number.

121720643 is a deficient number, since it is larger than the sum of its proper divisors (11065525).

121720643 is a wasteful number, since it uses less digits than its factorization.

121720643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11065524.

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 121720643 is about 11032.7078725035. The cubic root of 121720643 is about 495.5887196661.

Adding to 121720643 its reverse (346027121), we get a palindrome (467747764).

The spelling of 121720643 in words is "one hundred twenty-one million, seven hundred twenty thousand, six hundred forty-three".