1221011505 has 96 divisors (see below), whose sum is σ = 2537832960. Its totient is φ = 531256320.

The previous prime is 1221011503. The next prime is 1221011537. The reversal of 1221011505 is 5051101221.

It is not a de Polignac number, because 1221011505 - 2¹ = 1221011503 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1221011501) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 665940 + ... + 667770.

It is an arithmetic number, because the mean of its divisors is an integer number (26435760).

Almost surely, 2^1221011505 is an apocalyptic number.

1221011505 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221011505 is an abundant number, since it is smaller than the sum of its proper divisors (1316821455).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1221011505 is a wasteful number, since it uses less digits than its factorization.

1221011505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1951 (or 1948 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 18.

The square root of 1221011505 is about 34942.9750450645. The cubic root of 1221011505 is about 1068.8249554488.

Adding to 1221011505 its reverse (5051101221), we get a palindrome (6272112726).

The spelling of 1221011505 in words is "one billion, two hundred twenty-one million, eleven thousand, five hundred five".