21312121073 has 2 divisors, whose sum is σ = 21312121074. Its totient is φ = 21312121072.

The previous prime is 21312121021. The next prime is 21312121081. The reversal of 21312121073 is 37012121312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17183801569 + 4128319504 = 131087^2 + 64252^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312121073 - 2²⁴ = 21295343857 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21312124073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656060536 + 10656060537.

It is an arithmetic number, because the mean of its divisors is an integer number (10656060537).

Almost surely, 2^21312121073 is an apocalyptic number.

It is an amenable number.

21312121073 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312121073 is an equidigital number, since it uses as much as digits as its factorization.

21312121073 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 23.

Adding to 21312121073 its reverse (37012121312), we get a palindrome (58324242385).

The spelling of 21312121073 in words is "twenty-one billion, three hundred twelve million, one hundred twenty-one thousand, seventy-three".