1211221005 has 16 divisors (see below), whose sum is σ = 1938634560. Its totient is φ = 645757568.

The previous prime is 1211220991. The next prime is 1211221019. The reversal of 1211221005 is 5001221121.

It is an interprime number because it is at equal distance from previous prime (1211220991) and next prime (1211221019).

It is a cyclic number.

It is not a de Polignac number, because 1211221005 - 2⁷ = 1211220877 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35554 + ... + 60716.

It is an arithmetic number, because the mean of its divisors is an integer number (121164660).

Almost surely, 2^1211221005 is an apocalyptic number.

1211221005 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1211221005 is a deficient number, since it is larger than the sum of its proper divisors (727413555).

1211221005 is a wasteful number, since it uses less digits than its factorization.

1211221005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28380.

The product of its (nonzero) digits is 40, while the sum is 15.

The square root of 1211221005 is about 34802.6005493842. The cubic root of 1211221005 is about 1065.9605475814.

Adding to 1211221005 its reverse (5001221121), we get a palindrome (6212442126).

The spelling of 1211221005 in words is "one billion, two hundred eleven million, two hundred twenty-one thousand, five".