21311212361 has 2 divisors, whose sum is σ = 21311212362. Its totient is φ = 21311212360.

The previous prime is 21311212337. The next prime is 21311212367. The reversal of 21311212361 is 16321211312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18098589961 + 3212622400 = 134531^2 + 56680^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311212361 - 2⁶ = 21311212297 is a prime.

It is not a weakly prime, because it can be changed into another prime (21311212367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655606180 + 10655606181.

It is an arithmetic number, because the mean of its divisors is an integer number (10655606181).

Almost surely, 2^21311212361 is an apocalyptic number.

It is an amenable number.

21311212361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311212361 is an equidigital number, since it uses as much as digits as its factorization.

21311212361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 23.

Adding to 21311212361 its reverse (16321211312), we get a palindrome (37632423673).

The spelling of 21311212361 in words is "twenty-one billion, three hundred eleven million, two hundred twelve thousand, three hundred sixty-one".