1221121005 has 64 divisors (see below), whose sum is σ = 2155211520. Its totient is φ = 586745856.

The previous prime is 1221121003. The next prime is 1221121021. The reversal of 1221121005 is 5001211221.

It is not a de Polignac number, because 1221121005 - 2¹ = 1221121003 is a prime.

It is a super-2 number, since 2×1221121005² = 2982273017704420050, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221121001) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1551222 + ... + 1552008.

It is an arithmetic number, because the mean of its divisors is an integer number (33675180).

Almost surely, 2^1221121005 is an apocalyptic number.

1221121005 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221121005 is a deficient number, since it is larger than the sum of its proper divisors (934090515).

1221121005 is a wasteful number, since it uses less digits than its factorization.

1221121005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 990.

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

The square root of 1221121005 is about 34944.5418484776. The cubic root of 1221121005 is about 1068.8569051435.

Adding to 1221121005 its reverse (5001211221), we get a palindrome (6222332226).

The spelling of 1221121005 in words is "one billion, two hundred twenty-one million, one hundred twenty-one thousand, five".