21156211757 has 2 divisors, whose sum is σ = 21156211758. Its totient is φ = 21156211756.

The previous prime is 21156211753. The next prime is 21156211777. The reversal of 21156211757 is 75711265112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15400561801 + 5755649956 = 124099^2 + 75866^2 .

It is a cyclic number.

It is not a de Polignac number, because 21156211757 - 2² = 21156211753 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21156211757.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21156211753) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578105878 + 10578105879.

It is an arithmetic number, because the mean of its divisors is an integer number (10578105879).

Almost surely, 2^21156211757 is an apocalyptic number.

It is an amenable number.

21156211757 is a deficient number, since it is larger than the sum of its proper divisors (1).

21156211757 is an equidigital number, since it uses as much as digits as its factorization.

21156211757 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29400, while the sum is 38.

Adding to 21156211757 its reverse (75711265112), we get a palindrome (96867476869).

The spelling of 21156211757 in words is "twenty-one billion, one hundred fifty-six million, two hundred eleven thousand, seven hundred fifty-seven".