21989710823621 has 2 divisors, whose sum is σ = 21989710823622. Its totient is φ = 21989710823620.

The previous prime is 21989710823611. The next prime is 21989710823747. The reversal of 21989710823621 is 12632801798912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12524797043521 + 9464913780100 = 3539039^2 + 3076510^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21989710823621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21989710823611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994855411810 + 10994855411811.

It is an arithmetic number, because the mean of its divisors is an integer number (10994855411811).

Almost surely, 2^{21989710823621} is an apocalyptic number.

It is an amenable number.

21989710823621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21989710823621 is an equidigital number, since it uses as much as digits as its factorization.

21989710823621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5225472, while the sum is 59.

The spelling of 21989710823621 in words is "twenty-one trillion, nine hundred eighty-nine billion, seven hundred ten million, eight hundred twenty-three thousand, six hundred twenty-one".