21211221277 has 2 divisors, whose sum is σ = 21211221278. Its totient is φ = 21211221276.

The previous prime is 21211221223. The next prime is 21211221313. The reversal of 21211221277 is 77212211212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20031023961 + 1180197316 = 141531^2 + 34354^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211221277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21211221377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605610638 + 10605610639.

It is an arithmetic number, because the mean of its divisors is an integer number (10605610639).

Almost surely, 2^21211221277 is an apocalyptic number.

It is an amenable number.

21211221277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211221277 is an equidigital number, since it uses as much as digits as its factorization.

21211221277 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1568, while the sum is 28.

Adding to 21211221277 its reverse (77212211212), we get a palindrome (98423432489).

The spelling of 21211221277 in words is "twenty-one billion, two hundred eleven million, two hundred twenty-one thousand, two hundred seventy-seven".