20021641287521 has 2 divisors, whose sum is σ = 20021641287522. Its totient is φ = 20021641287520.

The previous prime is 20021641287491. The next prime is 20021641287559. The reversal of 20021641287521 is 12578214612002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18895843894225 + 1125797393296 = 4346935^2 + 1061036^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20021641287521 is a prime.

It is a super-2 number, since 2×20021641287521² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20021641287421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010820643760 + 10010820643761.

It is an arithmetic number, because the mean of its divisors is an integer number (10010820643761).

Almost surely, 2^{20021641287521} is an apocalyptic number.

It is an amenable number.

20021641287521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021641287521 is an equidigital number, since it uses as much as digits as its factorization.

20021641287521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 107520, while the sum is 41.

Adding to 20021641287521 its reverse (12578214612002), we get a palindrome (32599855899523).

The spelling of 20021641287521 in words is "twenty trillion, twenty-one billion, six hundred forty-one million, two hundred eighty-seven thousand, five hundred twenty-one".