2121605161721 has 2 divisors, whose sum is σ = 2121605161722. Its totient is φ = 2121605161720.

The previous prime is 2121605161703. The next prime is 2121605161747. The reversal of 2121605161721 is 1271615061212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2068594704121 + 53010457600 = 1438261^2 + 230240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2121605161721 is a prime.

It is not a weakly prime, because it can be changed into another prime (2121605169721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1060802580860 + 1060802580861.

It is an arithmetic number, because the mean of its divisors is an integer number (1060802580861).

Almost surely, 2^{2121605161721} is an apocalyptic number.

It is an amenable number.

2121605161721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2121605161721 is an equidigital number, since it uses as much as digits as its factorization.

2121605161721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 35.

The spelling of 2121605161721 in words is "two trillion, one hundred twenty-one billion, six hundred five million, one hundred sixty-one thousand, seven hundred twenty-one".