20121221381 has 2 divisors, whose sum is σ = 20121221382. Its totient is φ = 20121221380.

The previous prime is 20121221363. The next prime is 20121221413. The reversal of 20121221381 is 18312212102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17793158881 + 2328062500 = 133391^2 + 48250^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121221381 - 2³⁰ = 19047479557 is a prime.

It is a super-2 number, since 2×20121221381² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20121221311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10060610690 + 10060610691.

It is an arithmetic number, because the mean of its divisors is an integer number (10060610691).

Almost surely, 2^20121221381 is an apocalyptic number.

It is an amenable number.

20121221381 is a deficient number, since it is larger than the sum of its proper divisors (1).

20121221381 is an equidigital number, since it uses as much as digits as its factorization.

20121221381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 384, while the sum is 23.

Adding to 20121221381 its reverse (18312212102), we get a palindrome (38433433483).

The spelling of 20121221381 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, three hundred eighty-one".