21320020121 has 2 divisors, whose sum is σ = 21320020122. Its totient is φ = 21320020120.

The previous prime is 21320020091. The next prime is 21320020123. The reversal of 21320020121 is 12102002312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18731754496 + 2588265625 = 136864^2 + 50875^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21320020121 is a prime.

Together with 21320020123, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21320020096 and 21320020105.

It is not a weakly prime, because it can be changed into another prime (21320020123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660010060 + 10660010061.

It is an arithmetic number, because the mean of its divisors is an integer number (10660010061).

Almost surely, 2^21320020121 is an apocalyptic number.

It is an amenable number.

21320020121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320020121 is an equidigital number, since it uses as much as digits as its factorization.

21320020121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 14.

Adding to 21320020121 its reverse (12102002312), we get a palindrome (33422022433).

The spelling of 21320020121 in words is "twenty-one billion, three hundred twenty million, twenty thousand, one hundred twenty-one".