121720 has 32 divisors (see below), whose sum is σ = 291600. Its totient is φ = 45568.

The previous prime is 121711. The next prime is 121721. The reversal of 121720 is 27121.

121720 = T₁₅₁ + T₁₅₂ + ... + T₁₆₀.

It is a self number, because there is not a number n which added to its sum of digits gives 121720.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121721) by changing a digit.

121720 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 591 + ... + 769.

2¹²¹⁷²⁰ is an apocalyptic number.

121720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 121720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (145800).

121720 is an abundant number, since it is smaller than the sum of its proper divisors (169880).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

121720 is a wasteful number, since it uses less digits than its factorization.

121720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207 (or 203 counting only the distinct ones).

The product of its (nonzero) digits is 28, while the sum is 13.

The square root of 121720 is about 348.8839348551. The cubic root of 121720 is about 49.5587847001.

Adding to 121720 its reverse (27121), we get a palindrome (148841).

It can be divided in two parts, 121 and 720, that added together give a square (841 = 29²).

The spelling of 121720 in words is "one hundred twenty-one thousand, seven hundred twenty", and thus it is an iban number.