1221361031521 has 2 divisors, whose sum is σ = 1221361031522. Its totient is φ = 1221361031520.

The previous prime is 1221361031497. The next prime is 1221361031551. The reversal of 1221361031521 is 1251301631221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1112685315921 + 108675715600 = 1054839^2 + 329660^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221361031521 - 2¹⁹ = 1221360507233 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1221361031521.

It is not a weakly prime, because it can be changed into another prime (1221361031551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610680515760 + 610680515761.

It is an arithmetic number, because the mean of its divisors is an integer number (610680515761).

Almost surely, 2^{1221361031521} is an apocalyptic number.

It is an amenable number.

1221361031521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221361031521 is an equidigital number, since it uses as much as digits as its factorization.

1221361031521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 28.

Adding to 1221361031521 its reverse (1251301631221), we get a palindrome (2472662662742).

The spelling of 1221361031521 in words is "one trillion, two hundred twenty-one billion, three hundred sixty-one million, thirty-one thousand, five hundred twenty-one".