2121022021721 has 2 divisors, whose sum is σ = 2121022021722. Its totient is φ = 2121022021720.

The previous prime is 2121022021693. The next prime is 2121022021757. The reversal of 2121022021721 is 1271202201212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1480757994496 + 640264027225 = 1216864^2 + 800165^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2121022021721 is a prime.

It is not a weakly prime, because it can be changed into another prime (2121022021771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1060511010860 + 1060511010861.

It is an arithmetic number, because the mean of its divisors is an integer number (1060511010861).

Almost surely, 2^{2121022021721} is an apocalyptic number.

It is an amenable number.

2121022021721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2121022021721 is an equidigital number, since it uses as much as digits as its factorization.

2121022021721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 23.

Adding to 2121022021721 its reverse (1271202201212), we get a palindrome (3392224222933).

The spelling of 2121022021721 in words is "two trillion, one hundred twenty-one billion, twenty-two million, twenty-one thousand, seven hundred twenty-one".