21661165732429 has 2 divisors, whose sum is σ = 21661165732430. Its totient is φ = 21661165732428.

The previous prime is 21661165732387. The next prime is 21661165732447. The reversal of 21661165732429 is 92423756116612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21493330488100 + 167835244329 = 4636090^2 + 409677^2 .

It is a cyclic number.

It is not a de Polignac number, because 21661165732429 - 2¹⁹ = 21661165208141 is a prime.

It is a super-2 number, since 2×21661165732429² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21661165732429.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21661165739429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830582866214 + 10830582866215.

It is an arithmetic number, because the mean of its divisors is an integer number (10830582866215).

Almost surely, 2^{21661165732429} is an apocalyptic number.

It is an amenable number.

21661165732429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661165732429 is an equidigital number, since it uses as much as digits as its factorization.

21661165732429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6531840, while the sum is 55.

The spelling of 21661165732429 in words is "twenty-one trillion, six hundred sixty-one billion, one hundred sixty-five million, seven hundred thirty-two thousand, four hundred twenty-nine".