21221352511621 has 2 divisors, whose sum is σ = 21221352511622. Its totient is φ = 21221352511620.

The previous prime is 21221352511607. The next prime is 21221352511643. The reversal of 21221352511621 is 12611525312212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19816617915396 + 1404734596225 = 4451586^2 + 1185215^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221352511621 - 2⁵ = 21221352511589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221352511721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610676255810 + 10610676255811.

It is an arithmetic number, because the mean of its divisors is an integer number (10610676255811).

Almost surely, 2^{21221352511621} is an apocalyptic number.

It is an amenable number.

21221352511621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221352511621 is an equidigital number, since it uses as much as digits as its factorization.

21221352511621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14400, while the sum is 34.

Adding to 21221352511621 its reverse (12611525312212), we get a palindrome (33832877823833).

The spelling of 21221352511621 in words is "twenty-one trillion, two hundred twenty-one billion, three hundred fifty-two million, five hundred eleven thousand, six hundred twenty-one".