7216571721661 has 2 divisors, whose sum is σ = 7216571721662. Its totient is φ = 7216571721660.

The previous prime is 7216571721659. The next prime is 7216571721683. The reversal of 7216571721661 is 1661271756127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5292231235225 + 1924340486436 = 2300485^2 + 1387206^2 .

It is an emirp because it is prime and its reverse (1661271756127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7216571721661 - 2¹ = 7216571721659 is a prime.

Together with 7216571721659, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 7216571721599 and 7216571721608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7216571721361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3608285860830 + 3608285860831.

It is an arithmetic number, because the mean of its divisors is an integer number (3608285860831).

Almost surely, 2^{7216571721661} is an apocalyptic number.

It is an amenable number.

7216571721661 is a deficient number, since it is larger than the sum of its proper divisors (1).

7216571721661 is an equidigital number, since it uses as much as digits as its factorization.

7216571721661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1481760, while the sum is 52.

The spelling of 7216571721661 in words is "seven trillion, two hundred sixteen billion, five hundred seventy-one million, seven hundred twenty-one thousand, six hundred sixty-one".