21171190423661 has 2 divisors, whose sum is σ = 21171190423662. Its totient is φ = 21171190423660.

The previous prime is 21171190423631. The next prime is 21171190423723. The reversal of 21171190423661 is 16632409117112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19421737140100 + 1749453283561 = 4407010^2 + 1322669^2 .

It is a cyclic number.

It is not a de Polignac number, because 21171190423661 - 2³⁰ = 21170116681837 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21171190423631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585595211830 + 10585595211831.

It is an arithmetic number, because the mean of its divisors is an integer number (10585595211831).

Almost surely, 2^{21171190423661} is an apocalyptic number.

It is an amenable number.

21171190423661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21171190423661 is an equidigital number, since it uses as much as digits as its factorization.

21171190423661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108864, while the sum is 44.

The spelling of 21171190423661 in words is "twenty-one trillion, one hundred seventy-one billion, one hundred ninety million, four hundred twenty-three thousand, six hundred sixty-one".