21126684457 has 2 divisors, whose sum is σ = 21126684458. Its totient is φ = 21126684456.

The previous prime is 21126684413. The next prime is 21126684529. The reversal of 21126684457 is 75448662112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19179757081 + 1946927376 = 138491^2 + 44124^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21126684457 is a prime.

It is a super-2 number, since 2×21126684457² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21126084457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10563342228 + 10563342229.

It is an arithmetic number, because the mean of its divisors is an integer number (10563342229).

Almost surely, 2^21126684457 is an apocalyptic number.

It is an amenable number.

21126684457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21126684457 is an equidigital number, since it uses as much as digits as its factorization.

21126684457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 645120, while the sum is 46.

The spelling of 21126684457 in words is "twenty-one billion, one hundred twenty-six million, six hundred eighty-four thousand, four hundred fifty-seven".