1221517261 has 2 divisors, whose sum is σ = 1221517262. Its totient is φ = 1221517260.

The previous prime is 1221517259. The next prime is 1221517279. The reversal of 1221517261 is 1627151221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 898200900 + 323316361 = 29970^2 + 17981^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221517261 - 2¹ = 1221517259 is a prime.

Together with 1221517259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221517291) 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, 610758630 + 610758631.

It is an arithmetic number, because the mean of its divisors is an integer number (610758631).

Almost surely, 2^1221517261 is an apocalyptic number.

It is an amenable number.

1221517261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221517261 is an equidigital number, since it uses as much as digits as its factorization.

1221517261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 28.

The square root of 1221517261 is about 34950.2111724665. The cubic root of 1221517261 is about 1068.9725079803.

Adding to 1221517261 its reverse (1627151221), we get a palindrome (2848668482).

The spelling of 1221517261 in words is "one billion, two hundred twenty-one million, five hundred seventeen thousand, two hundred sixty-one".