20979691 has 2 divisors, whose sum is σ = 20979692. Its totient is φ = 20979690.

The previous prime is 20979677. The next prime is 20979697. The reversal of 20979691 is 19697902.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20979691 is a prime.

It is not a weakly prime, because it can be changed into another prime (20979697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10489845 + 10489846.

It is an arithmetic number, because the mean of its divisors is an integer number (10489846).

Almost surely, 2^20979691 is an apocalyptic number.

20979691 is a deficient number, since it is larger than the sum of its proper divisors (1).

20979691 is an equidigital number, since it uses as much as digits as its factorization.

20979691 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 61236, while the sum is 43.

The square root of 20979691 is about 4580.3592653852. The cubic root of 20979691 is about 275.8034508711.

The spelling of 20979691 in words is "twenty million, nine hundred seventy-nine thousand, six hundred ninety-one".