1221242155 has 32 divisors (see below), whose sum is σ = 1754763264. Its totient is φ = 797761536.

The previous prime is 1221242153. The next prime is 1221242159. The reversal of 1221242155 is 5512421221.

It is a cyclic number.

It is not a de Polignac number, because 1221242155 - 2¹ = 1221242153 is a prime.

It is a super-2 number, since 2×1221242155² = 2982864802298088050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221242153) 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, 203934 + ... + 209836.

It is an arithmetic number, because the mean of its divisors is an integer number (54836352).

Almost surely, 2^1221242155 is an apocalyptic number.

1221242155 is a deficient number, since it is larger than the sum of its proper divisors (533521109).

1221242155 is a wasteful number, since it uses less digits than its factorization.

1221242155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6195.

The product of its digits is 1600, while the sum is 25.

The square root of 1221242155 is about 34946.2752664715. The cubic root of 1221242155 is about 1068.8922518267.

Adding to 1221242155 its reverse (5512421221), we get a palindrome (6733663376).

The spelling of 1221242155 in words is "one billion, two hundred twenty-one million, two hundred forty-two thousand, one hundred fifty-five".