21106961 has 2 divisors, whose sum is σ = 21106962. Its totient is φ = 21106960.

The previous prime is 21106957. The next prime is 21106993. The reversal of 21106961 is 16960112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17977600 + 3129361 = 4240^2 + 1769^2 .

It is a cyclic number.

It is not a de Polignac number, because 21106961 - 2² = 21106957 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21106961.

It is not a weakly prime, because it can be changed into another prime (21106361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553480 + 10553481.

It is an arithmetic number, because the mean of its divisors is an integer number (10553481).

Almost surely, 2^21106961 is an apocalyptic number.

It is an amenable number.

21106961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21106961 is an equidigital number, since it uses as much as digits as its factorization.

21106961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21106961 is about 4594.2312741089. The cubic root of 21106961 is about 276.3600330150.

The spelling of 21106961 in words is "twenty-one million, one hundred six thousand, nine hundred sixty-one".