1221006553 has 4 divisors (see below), whose sum is σ = 1314930148. Its totient is φ = 1127082960.

The previous prime is 1221006551. The next prime is 1221006581. The reversal of 1221006553 is 3556001221.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 834805449 + 386201104 = 28893^2 + 19652^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221006553 - 2¹ = 1221006551 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221006551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46961778 + ... + 46961803.

It is an arithmetic number, because the mean of its divisors is an integer number (328732537).

Almost surely, 2^1221006553 is an apocalyptic number.

1221006553 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1221006553 is a deficient number, since it is larger than the sum of its proper divisors (93923595).

1221006553 is an equidigital number, since it uses as much as digits as its factorization.

1221006553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93923594.

The product of its (nonzero) digits is 1800, while the sum is 25.

The square root of 1221006553 is about 34942.9041866872. The cubic root of 1221006553 is about 1068.8235105189.

Adding to 1221006553 its reverse (3556001221), we get a palindrome (4777007774).

The spelling of 1221006553 in words is "one billion, two hundred twenty-one million, six thousand, five hundred fifty-three".