1213521221 has 6 divisors (see below), whose sum is σ = 1333870566. Its totient is φ = 1103201000.

The previous prime is 1213521173. The next prime is 1213521233. The reversal of 1213521221 is 1221253121.

It can be written as a sum of positive squares in only one way, i.e., 1204437025 + 9084196 = 34705^2 + 3014^2 .

It is not a de Polignac number, because 1213521221 - 2¹⁴ = 1213504837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1213521193 and 1213521202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1213521271) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5014430 + ... + 5014671.

It is an arithmetic number, because the mean of its divisors is an integer number (222311761).

Almost surely, 2^1213521221 is an apocalyptic number.

1213521221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1213521221 is a deficient number, since it is larger than the sum of its proper divisors (120349345).

1213521221 is a wasteful number, since it uses less digits than its factorization.

1213521221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10029123 (or 10029112 counting only the distinct ones).

The product of its digits is 240, while the sum is 20.

The square root of 1213521221 is about 34835.6314855924. The cubic root of 1213521221 is about 1066.6349053802.

Adding to 1213521221 its reverse (1221253121), we get a palindrome (2434774342).

The spelling of 1213521221 in words is "one billion, two hundred thirteen million, five hundred twenty-one thousand, two hundred twenty-one".