21120931666657 has 2 divisors, whose sum is σ = 21120931666658. Its totient is φ = 21120931666656.

The previous prime is 21120931666631. The next prime is 21120931666661. The reversal of 21120931666657 is 75666613902112.

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., 11263648850496 + 9857282816161 = 3356136^2 + 3139631^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21120931666657 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21120931666598 and 21120931666607.

It is not a weakly prime, because it can be changed into another prime (21120931666957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560465833328 + 10560465833329.

It is an arithmetic number, because the mean of its divisors is an integer number (10560465833329).

Almost surely, 2^{21120931666657} is an apocalyptic number.

It is an amenable number.

21120931666657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120931666657 is an equidigital number, since it uses as much as digits as its factorization.

21120931666657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4898880, while the sum is 55.

The spelling of 21120931666657 in words is "twenty-one trillion, one hundred twenty billion, nine hundred thirty-one million, six hundred sixty-six thousand, six hundred fifty-seven".