21551214121 has 2 divisors, whose sum is σ = 21551214122. Its totient is φ = 21551214120.

The previous prime is 21551214089. The next prime is 21551214133. The reversal of 21551214121 is 12141215512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11836352025 + 9714862096 = 108795^2 + 98564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551214121 - 2⁵ = 21551214089 is a prime.

It is not a weakly prime, because it can be changed into another prime (27551214121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775607060 + 10775607061.

It is an arithmetic number, because the mean of its divisors is an integer number (10775607061).

Almost surely, 2^21551214121 is an apocalyptic number.

It is an amenable number.

21551214121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551214121 is an equidigital number, since it uses as much as digits as its factorization.

21551214121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 800, while the sum is 25.

Adding to 21551214121 its reverse (12141215512), we get a palindrome (33692429633).

The spelling of 21551214121 in words is "twenty-one billion, five hundred fifty-one million, two hundred fourteen thousand, one hundred twenty-one".