1221015566 has 8 divisors (see below), whose sum is σ = 1832307480. Its totient is φ = 610246408.

The previous prime is 1221015557. The next prime is 1221015581. The reversal of 1221015566 is 6655101221.

It is a happy number.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 124796 + ... + 134223.

It is an arithmetic number, because the mean of its divisors is an integer number (229038435).

Almost surely, 2^1221015566 is an apocalyptic number.

1221015566 is a deficient number, since it is larger than the sum of its proper divisors (611291914).

1221015566 is a wasteful number, since it uses less digits than its factorization.

1221015566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261378.

The product of its (nonzero) digits is 3600, while the sum is 29.

The square root of 1221015566 is about 34943.0331539779. The cubic root of 1221015566 is about 1068.8261403935.

Adding to 1221015566 its reverse (6655101221), we get a palindrome (7876116787).

The spelling of 1221015566 in words is "one billion, two hundred twenty-one million, fifteen thousand, five hundred sixty-six".