1221355605 has 16 divisors (see below), whose sum is σ = 1955891520. Its totient is φ = 650815488.

The previous prime is 1221355589. The next prime is 1221355621. The reversal of 1221355605 is 5065531221.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1221355589) and next prime (1221355621).

It is not a de Polignac number, because 1221355605 - 2⁴ = 1221355589 is a prime.

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 15 ways as a sum of consecutive naturals, for example, 18015 + ... + 52604.

It is an arithmetic number, because the mean of its divisors is an integer number (122243220).

Almost surely, 2^1221355605 is an apocalyptic number.

1221355605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221355605 is a deficient number, since it is larger than the sum of its proper divisors (734535915).

1221355605 is a wasteful number, since it uses less digits than its factorization.

1221355605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71780.

The product of its (nonzero) digits is 9000, while the sum is 30.

The square root of 1221355605 is about 34947.8984346699. The cubic root of 1221355605 is about 1068.9253498410.

Adding to 1221355605 its reverse (5065531221), we get a palindrome (6286886826).

The spelling of 1221355605 in words is "one billion, two hundred twenty-one million, three hundred fifty-five thousand, six hundred five".