21744051207661 has 2 divisors, whose sum is σ = 21744051207662. Its totient is φ = 21744051207660.

The previous prime is 21744051207623. The next prime is 21744051207689. The reversal of 21744051207661 is 16670215044712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20790918806436 + 953132401225 = 4559706^2 + 976285^2 .

It is a cyclic number.

It is not a de Polignac number, because 21744051207661 - 2²⁷ = 21743916989933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21744051207761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10872025603830 + 10872025603831.

It is an arithmetic number, because the mean of its divisors is an integer number (10872025603831).

Almost surely, 2^{21744051207661} is an apocalyptic number.

It is an amenable number.

21744051207661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21744051207661 is an equidigital number, since it uses as much as digits as its factorization.

21744051207661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 564480, while the sum is 46.

The spelling of 21744051207661 in words is "twenty-one trillion, seven hundred forty-four billion, fifty-one million, two hundred seven thousand, six hundred sixty-one".