1221661221 has 32 divisors (see below), whose sum is σ = 1935014400. Its totient is φ = 677234880.

The previous prime is 1221661219. The next prime is 1221661229.

1221661221 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1221661221 - 2¹ = 1221661219 is a prime.

It is a super-2 number, since 2×1221661221² = 2984912277790421682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1221661191 and 1221661200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221661229) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 15411 + ... + 51776.

It is an arithmetic number, because the mean of its divisors is an integer number (60469200).

Almost surely, 2^1221661221 is an apocalyptic number.

1221661221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221661221 is a deficient number, since it is larger than the sum of its proper divisors (713353179).

1221661221 is a wasteful number, since it uses less digits than its factorization.

1221661221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67249.

The product of its digits is 576, while the sum is 24.

The square root of 1221661221 is about 34952.2706129373. The cubic root of 1221661221 is about 1069.0145003565.

It can be divided in two parts, 12216 and 61221, that added together give a palindrome (73437).

The spelling of 1221661221 in words is "one billion, two hundred twenty-one million, six hundred sixty-one thousand, two hundred twenty-one".