21020243881261 has 2 divisors, whose sum is σ = 21020243881262. Its totient is φ = 21020243881260.

The previous prime is 21020243881229. The next prime is 21020243881267. The reversal of 21020243881261 is 16218834202012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17840908822500 + 3179335058761 = 4223850^2 + 1783069^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020243881261 - 2⁵ = 21020243881229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020243881267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510121940630 + 10510121940631.

It is an arithmetic number, because the mean of its divisors is an integer number (10510121940631).

Almost surely, 2^{21020243881261} is an apocalyptic number.

It is an amenable number.

21020243881261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020243881261 is an equidigital number, since it uses as much as digits as its factorization.

21020243881261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 73728, while the sum is 40.

The spelling of 21020243881261 in words is "twenty-one trillion, twenty billion, two hundred forty-three million, eight hundred eighty-one thousand, two hundred sixty-one".