72121 has 4 divisors (see below), whose sum is σ = 82432. Its totient is φ = 61812.

The previous prime is 72109. The next prime is 72139. The reversal of 72121 is 12127.

72121 is an esthetic number in base 4, because in such base its adjacent digits differ by 1.

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: 12127 = 67 ⋅181.

It is a cyclic number.

It is not a de Polignac number, because 72121 - 2⁵ = 72089 is a prime.

It is an alternating number because its digits alternate between odd and even.

72121 is a modest number, since divided by 2121 gives 7 as remainder.

It is not an unprimeable number, because it can be changed into a prime (72101) 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, 5145 + ... + 5158.

It is an arithmetic number, because the mean of its divisors is an integer number (20608).

2⁷²¹²¹ is an apocalyptic number.

It is an amenable number.

72121 is a deficient number, since it is larger than the sum of its proper divisors (10311).

72121 is a wasteful number, since it uses less digits than its factorization.

72121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10310.

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

The square root of 72121 is about 268.5535328384. The cubic root of 72121 is about 41.6249680611.

Adding to 72121 its reverse (12127), we get a palindrome (84248).

The spelling of 72121 in words is "seventy-two thousand, one hundred twenty-one", and thus it is an iban number.