19947979 has 2 divisors, whose sum is σ = 19947980. Its totient is φ = 19947978.

The previous prime is 19947913. The next prime is 19947997. The reversal of 19947979 is 97974991.

Together with next prime (19947997) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19947979 is a prime.

It is not a weakly prime, because it can be changed into another prime (19947079) 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, 9973989 + 9973990.

It is an arithmetic number, because the mean of its divisors is an integer number (9973990).

Almost surely, 2^19947979 is an apocalyptic number.

19947979 is a deficient number, since it is larger than the sum of its proper divisors (1).

19947979 is an equidigital number, since it uses as much as digits as its factorization.

19947979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1285956, while the sum is 55.

The square root of 19947979 is about 4466.3160434524. The cubic root of 19947979 is about 271.2062127851.

The spelling of 19947979 in words is "nineteen million, nine hundred forty-seven thousand, nine hundred seventy-nine".