7720621 has 2 divisors, whose sum is σ = 7720622. Its totient is φ = 7720620.

The previous prime is 7720619. The next prime is 7720633. The reversal of 7720621 is 1260277.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6056521 + 1664100 = 2461^2 + 1290^2 .

It is an emirp because it is prime and its reverse (1260277) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7720621 - 2¹ = 7720619 is a prime.

Together with 7720619, it forms a pair of twin primes.

It is an Ulam number.

7720621 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7720021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3860310 + 3860311.

It is an arithmetic number, because the mean of its divisors is an integer number (3860311).

Almost surely, 2^7720621 is an apocalyptic number.

It is an amenable number.

7720621 is a deficient number, since it is larger than the sum of its proper divisors (1).

7720621 is an equidigital number, since it uses as much as digits as its factorization.

7720621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 7720621 is about 2778.6005470380. The cubic root of 7720621 is about 197.6442016897.

Adding to 7720621 its reverse (1260277), we get a palindrome (8980898).

The spelling of 7720621 in words is "seven million, seven hundred twenty thousand, six hundred twenty-one".