215667841661 has 2 divisors, whose sum is σ = 215667841662. Its totient is φ = 215667841660.

The previous prime is 215667841621. The next prime is 215667841687. The reversal of 215667841661 is 166148766512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 142416419161 + 73251422500 = 377381^2 + 270650^2 .

It is a cyclic number.

It is not a de Polignac number, because 215667841661 - 2³⁴ = 198487972477 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215667841601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107833920830 + 107833920831.

It is an arithmetic number, because the mean of its divisors is an integer number (107833920831).

Almost surely, 2^215667841661 is an apocalyptic number.

It is an amenable number.

215667841661 is a deficient number, since it is larger than the sum of its proper divisors (1).

215667841661 is an equidigital number, since it uses as much as digits as its factorization.

215667841661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2903040, while the sum is 53.

The spelling of 215667841661 in words is "two hundred fifteen billion, six hundred sixty-seven million, eight hundred forty-one thousand, six hundred sixty-one".