1221666523 has 16 divisors (see below), whose sum is σ = 1525708800. Its totient is φ = 950328000.

The previous prime is 1221666517. The next prime is 1221666539. The reversal of 1221666523 is 3256661221.

It is a cyclic number.

It is not a de Polignac number, because 1221666523 - 2¹³ = 1221658331 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1221666553) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33078 + ... + 59476.

It is an arithmetic number, because the mean of its divisors is an integer number (95356800).

Almost surely, 2^1221666523 is an apocalyptic number.

1221666523 is a deficient number, since it is larger than the sum of its proper divisors (304042277).

1221666523 is a wasteful number, since it uses less digits than its factorization.

1221666523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27018.

The product of its digits is 25920, while the sum is 34.

The square root of 1221666523 is about 34952.3464591435. The cubic root of 1221666523 is about 1069.0160468591.

The spelling of 1221666523 in words is "one billion, two hundred twenty-one million, six hundred sixty-six thousand, five hundred twenty-three".