21251749546957 has 2 divisors, whose sum is σ = 21251749546958. Its totient is φ = 21251749546956.

The previous prime is 21251749546913. The next prime is 21251749546981. The reversal of 21251749546957 is 75964594715212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19567272627081 + 1684476919876 = 4423491^2 + 1297874^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21251749546957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21251749546892 and 21251749546901.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21251749546987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625874773478 + 10625874773479.

It is an arithmetic number, because the mean of its divisors is an integer number (10625874773479).

Almost surely, 2^{21251749546957} is an apocalyptic number.

It is an amenable number.

21251749546957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21251749546957 is an equidigital number, since it uses as much as digits as its factorization.

21251749546957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 190512000, while the sum is 67.

The spelling of 21251749546957 in words is "twenty-one trillion, two hundred fifty-one billion, seven hundred forty-nine million, five hundred forty-six thousand, nine hundred fifty-seven".