18211170807521 has 2 divisors, whose sum is σ = 18211170807522. Its totient is φ = 18211170807520.

The previous prime is 18211170807499. The next prime is 18211170807547. The reversal of 18211170807521 is 12570807111281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16963401382225 + 1247769425296 = 4118665^2 + 1117036^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18211170807521 is a prime.

It is not a weakly prime, because it can be changed into another prime (18211170107521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9105585403760 + 9105585403761.

It is an arithmetic number, because the mean of its divisors is an integer number (9105585403761).

Almost surely, 2^{18211170807521} is an apocalyptic number.

It is an amenable number.

18211170807521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18211170807521 is an equidigital number, since it uses as much as digits as its factorization.

18211170807521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62720, while the sum is 44.

The spelling of 18211170807521 in words is "eighteen trillion, two hundred eleven billion, one hundred seventy million, eight hundred seven thousand, five hundred twenty-one".