21231320121997 has 2 divisors, whose sum is σ = 21231320121998. Its totient is φ = 21231320121996.

The previous prime is 21231320121959. The next prime is 21231320122013. The reversal of 21231320121997 is 79912102313212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16254008203876 + 4977311918121 = 4031626^2 + 2230989^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231320121997 - 2¹¹ = 21231320119949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21231320121937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615660060998 + 10615660060999.

It is an arithmetic number, because the mean of its divisors is an integer number (10615660060999).

Almost surely, 2^{21231320121997} is an apocalyptic number.

It is an amenable number.

21231320121997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231320121997 is an equidigital number, since it uses as much as digits as its factorization.

21231320121997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81648, while the sum is 43.

The spelling of 21231320121997 in words is "twenty-one trillion, two hundred thirty-one billion, three hundred twenty million, one hundred twenty-one thousand, nine hundred ninety-seven".