19857979 has 2 divisors, whose sum is σ = 19857980. Its totient is φ = 19857978.

The previous prime is 19857977. The next prime is 19857997. The reversal of 19857979 is 97975891.

Together with next prime (19857997) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19857979 - 2¹ = 19857977 is a prime.

Together with 19857977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (19857973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9928989 + 9928990.

It is an arithmetic number, because the mean of its divisors is an integer number (9928990).

Almost surely, 2^19857979 is an apocalyptic number.

19857979 is a deficient number, since it is larger than the sum of its proper divisors (1).

19857979 is an equidigital number, since it uses as much as digits as its factorization.

19857979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1428840, while the sum is 55.

The square root of 19857979 is about 4456.2292355757. The cubic root of 19857979 is about 270.7977276322.

The spelling of 19857979 in words is "nineteen million, eight hundred fifty-seven thousand, nine hundred seventy-nine".