1221166166221 has 8 divisors (see below), whose sum is σ = 1233319647384. Its totient is φ = 1209013915200.

The previous prime is 1221166166203. The next prime is 1221166166257. The reversal of 1221166166221 is 1226616611221.

It can be written as a sum of positive squares in 4 ways, for example, as 1168537218121 + 52628948100 = 1080989^2 + 229410^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1221166166221 - 2¹³ = 1221166158029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221166166201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1756315 + ... + 2350951.

It is an arithmetic number, because the mean of its divisors is an integer number (154164955923).

Almost surely, 2^{1221166166221} is an apocalyptic number.

It is an amenable number.

1221166166221 is a deficient number, since it is larger than the sum of its proper divisors (12153481163).

1221166166221 is a wasteful number, since it uses less digits than its factorization.

1221166166221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 615071.

The product of its digits is 20736, while the sum is 37.

The spelling of 1221166166221 in words is "one trillion, two hundred twenty-one billion, one hundred sixty-six million, one hundred sixty-six thousand, two hundred twenty-one".