1221210100261 has 2 divisors, whose sum is σ = 1221210100262. Its totient is φ = 1221210100260.

The previous prime is 1221210100147. The next prime is 1221210100321. The reversal of 1221210100261 is 1620010121221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1147535855361 + 73674244900 = 1071231^2 + 271430^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221210100261 - 2³¹ = 1219062616613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221210100661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610605050130 + 610605050131.

It is an arithmetic number, because the mean of its divisors is an integer number (610605050131).

Almost surely, 2^{1221210100261} is an apocalyptic number.

It is an amenable number.

1221210100261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221210100261 is an equidigital number, since it uses as much as digits as its factorization.

1221210100261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 19.

Adding to 1221210100261 its reverse (1620010121221), we get a palindrome (2841220221482).

The spelling of 1221210100261 in words is "one trillion, two hundred twenty-one billion, two hundred ten million, one hundred thousand, two hundred sixty-one".