221642673556561 has 2 divisors, whose sum is σ = 221642673556562. Its totient is φ = 221642673556560.

The previous prime is 221642673556547. The next prime is 221642673556571. The reversal of 221642673556561 is 165655376246122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 153959555905936 + 67683117650625 = 12408044^2 + 8226975^2 .

It is a cyclic number.

It is not a de Polignac number, because 221642673556561 - 2¹⁷ = 221642673425489 is a prime.

It is a super-2 number, since 2×221642673556561² (a number of 29 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 221642673556561.

It is not a weakly prime, because it can be changed into another prime (221642673556571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110821336778280 + 110821336778281.

It is an arithmetic number, because the mean of its divisors is an integer number (110821336778281).

Almost surely, 2^{221642673556561} is an apocalyptic number.

It is an amenable number.

221642673556561 is a deficient number, since it is larger than the sum of its proper divisors (1).

221642673556561 is an equidigital number, since it uses as much as digits as its factorization.

221642673556561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864000, while the sum is 61.

The spelling of 221642673556561 in words is "two hundred twenty-one trillion, six hundred forty-two billion, six hundred seventy-three million, five hundred fifty-six thousand, five hundred sixty-one".