20421857873 has 2 divisors, whose sum is σ = 20421857874. Its totient is φ = 20421857872.

The previous prime is 20421857867. The next prime is 20421857881. The reversal of 20421857873 is 37875812402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19811125504 + 610732369 = 140752^2 + 24713^2 .

It is a cyclic number.

It is not a de Polignac number, because 20421857873 - 2⁴ = 20421857857 is a prime.

It is not a weakly prime, because it can be changed into another prime (20421857893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210928936 + 10210928937.

It is an arithmetic number, because the mean of its divisors is an integer number (10210928937).

Almost surely, 2^20421857873 is an apocalyptic number.

It is an amenable number.

20421857873 is a deficient number, since it is larger than the sum of its proper divisors (1).

20421857873 is an equidigital number, since it uses as much as digits as its factorization.

20421857873 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 752640, while the sum is 47.

The spelling of 20421857873 in words is "twenty billion, four hundred twenty-one million, eight hundred fifty-seven thousand, eight hundred seventy-three".