20709979 has 2 divisors, whose sum is σ = 20709980. Its totient is φ = 20709978.

The previous prime is 20709977. The next prime is 20709989. The reversal of 20709979 is 97990702.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20709979 - 2¹ = 20709977 is a prime.

Together with 20709977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20709977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10354989 + 10354990.

It is an arithmetic number, because the mean of its divisors is an integer number (10354990).

Almost surely, 2^20709979 is an apocalyptic number.

20709979 is a deficient number, since it is larger than the sum of its proper divisors (1).

20709979 is an equidigital number, since it uses as much as digits as its factorization.

20709979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 71442, while the sum is 43.

The square root of 20709979 is about 4550.8217939181. The cubic root of 20709979 is about 274.6164526362.

The spelling of 20709979 in words is "twenty million, seven hundred nine thousand, nine hundred seventy-nine".