1220561665 has 32 divisors (see below), whose sum is σ = 1592680320. Its totient is φ = 894372864.

The previous prime is 1220561663. The next prime is 1220561687. The reversal of 1220561665 is 5661650221.

It is a cyclic number.

It is not a de Polignac number, because 1220561665 - 2¹ = 1220561663 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1220561665.

It is not an unprimeable number, because it can be changed into a prime (1220561663) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1531047 + ... + 1531843.

It is an arithmetic number, because the mean of its divisors is an integer number (49771260).

Almost surely, 2^1220561665 is an apocalyptic number.

It is an amenable number.

1220561665 is a deficient number, since it is larger than the sum of its proper divisors (372118655).

1220561665 is a wasteful number, since it uses less digits than its factorization.

1220561665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1281.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 1220561665 is about 34936.5376790546. The cubic root of 1220561665 is about 1068.6936819725.

The spelling of 1220561665 in words is "one billion, two hundred twenty million, five hundred sixty-one thousand, six hundred sixty-five".