7720121 has 2 divisors, whose sum is σ = 7720122. Its totient is φ = 7720120.

The previous prime is 7720109. The next prime is 7720123. The reversal of 7720121 is 1210277.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7507600 + 212521 = 2740^2 + 461^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7720121 is a prime.

Together with 7720123, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 7720093 and 7720102.

It is not a weakly prime, because it can be changed into another prime (7720123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3860060 + 3860061.

It is an arithmetic number, because the mean of its divisors is an integer number (3860061).

Almost surely, 2^7720121 is an apocalyptic number.

It is an amenable number.

7720121 is a deficient number, since it is larger than the sum of its proper divisors (1).

7720121 is an equidigital number, since it uses as much as digits as its factorization.

7720121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 7720121 is about 2778.5105722311. The cubic root of 7720121 is about 197.6399350107.

Adding to 7720121 its reverse (1210277), we get a palindrome (8930398).

The spelling of 7720121 in words is "seven million, seven hundred twenty thousand, one hundred twenty-one".