661503505121 has 2 divisors, whose sum is σ = 661503505122. Its totient is φ = 661503505120.

The previous prime is 661503505109. The next prime is 661503505129. The reversal of 661503505121 is 121505305166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 635312614225 + 26190890896 = 797065^2 + 161836^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661503505121 is a prime.

It is not a weakly prime, because it can be changed into another prime (661503505129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330751752560 + 330751752561.

It is an arithmetic number, because the mean of its divisors is an integer number (330751752561).

Almost surely, 2^661503505121 is an apocalyptic number.

It is an amenable number.

661503505121 is a deficient number, since it is larger than the sum of its proper divisors (1).

661503505121 is an equidigital number, since it uses as much as digits as its factorization.

661503505121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27000, while the sum is 35.

The spelling of 661503505121 in words is "six hundred sixty-one billion, five hundred three million, five hundred five thousand, one hundred twenty-one".