21011020331621 has 2 divisors, whose sum is σ = 21011020331622. Its totient is φ = 21011020331620.

The previous prime is 21011020331557. The next prime is 21011020331647. The reversal of 21011020331621 is 12613302011012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14496713577025 + 6514306754596 = 3807455^2 + 2552314^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011020331621 - 2⁶ = 21011020331557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011020331681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505510165810 + 10505510165811.

It is an arithmetic number, because the mean of its divisors is an integer number (10505510165811).

Almost surely, 2^{21011020331621} is an apocalyptic number.

It is an amenable number.

21011020331621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011020331621 is an equidigital number, since it uses as much as digits as its factorization.

21011020331621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 23.

Adding to 21011020331621 its reverse (12613302011012), we get a palindrome (33624322342633).

The spelling of 21011020331621 in words is "twenty-one trillion, eleven billion, twenty million, three hundred thirty-one thousand, six hundred twenty-one".