21212120257 has 2 divisors, whose sum is σ = 21212120258. Its totient is φ = 21212120256.

The previous prime is 21212120183. The next prime is 21212120261. The reversal of 21212120257 is 75202121212.

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., 18587504896 + 2624615361 = 136336^2 + 51231^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212120257 - 2⁷ = 21212120129 is a prime.

It is not a weakly prime, because it can be changed into another prime (21212120057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606060128 + 10606060129.

It is an arithmetic number, because the mean of its divisors is an integer number (10606060129).

Almost surely, 2^21212120257 is an apocalyptic number.

It is an amenable number.

21212120257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212120257 is an equidigital number, since it uses as much as digits as its factorization.

21212120257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 25.

Adding to 21212120257 its reverse (75202121212), we get a palindrome (96414241469).

The spelling of 21212120257 in words is "twenty-one billion, two hundred twelve million, one hundred twenty thousand, two hundred fifty-seven".