21661465732057 has 2 divisors, whose sum is σ = 21661465732058. Its totient is φ = 21661465732056.

The previous prime is 21661465732031. The next prime is 21661465732073. The reversal of 21661465732057 is 75023756416612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21012790128841 + 648675603216 = 4583971^2 + 805404^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21661465732057 is a prime.

It is a super-2 number, since 2×21661465732057² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21661465731989 and 21661465732007.

It is not a weakly prime, because it can be changed into another prime (21661465730057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830732866028 + 10830732866029.

It is an arithmetic number, because the mean of its divisors is an integer number (10830732866029).

Almost surely, 2^{21661465732057} is an apocalyptic number.

It is an amenable number.

21661465732057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661465732057 is an equidigital number, since it uses as much as digits as its factorization.

21661465732057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12700800, while the sum is 55.

The spelling of 21661465732057 in words is "twenty-one trillion, six hundred sixty-one billion, four hundred sixty-five million, seven hundred thirty-two thousand, fifty-seven".