21020873221 has 2 divisors, whose sum is σ = 21020873222. Its totient is φ = 21020873220.

The previous prime is 21020873189. The next prime is 21020873257. The reversal of 21020873221 is 12237802012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14522901121 + 6497972100 = 120511^2 + 80610^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020873221 - 2⁵ = 21020873189 is a prime.

It is a super-2 number, since 2×21020873221² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21020873221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020813221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510436610 + 10510436611.

It is an arithmetic number, because the mean of its divisors is an integer number (10510436611).

Almost surely, 2^21020873221 is an apocalyptic number.

It is an amenable number.

21020873221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020873221 is an equidigital number, since it uses as much as digits as its factorization.

21020873221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2688, while the sum is 28.

The spelling of 21020873221 in words is "twenty-one billion, twenty million, eight hundred seventy-three thousand, two hundred twenty-one".