1221550756681 has 2 divisors, whose sum is σ = 1221550756682. Its totient is φ = 1221550756680.

The previous prime is 1221550756639. The next prime is 1221550756693. The reversal of 1221550756681 is 1866570551221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1032847396681 + 188703360000 = 1016291^2 + 434400^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221550756681 - 2²⁹ = 1221013885769 is a prime.

It is a super-2 number, since 2×1221550756681² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1221550756081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610775378340 + 610775378341.

It is an arithmetic number, because the mean of its divisors is an integer number (610775378341).

Almost surely, 2^{1221550756681} is an apocalyptic number.

It is an amenable number.

1221550756681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221550756681 is an equidigital number, since it uses as much as digits as its factorization.

1221550756681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008000, while the sum is 49.

The spelling of 1221550756681 in words is "one trillion, two hundred twenty-one billion, five hundred fifty million, seven hundred fifty-six thousand, six hundred eighty-one".