19971857 has 2 divisors, whose sum is σ = 19971858. Its totient is φ = 19971856.

The previous prime is 19971761. The next prime is 19971859. The reversal of 19971857 is 75817991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 3682561 = 4036^2 + 1919^2 .

It is a cyclic number.

It is not a de Polignac number, because 19971857 - 2¹⁰ = 19970833 is a prime.

Together with 19971859, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19971859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9985928 + 9985929.

It is an arithmetic number, because the mean of its divisors is an integer number (9985929).

Almost surely, 2^19971857 is an apocalyptic number.

It is an amenable number.

19971857 is a deficient number, since it is larger than the sum of its proper divisors (1).

19971857 is an equidigital number, since it uses as much as digits as its factorization.

19971857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 158760, while the sum is 47.

The square root of 19971857 is about 4468.9883642722. The cubic root of 19971857 is about 271.3143821351.

The spelling of 19971857 in words is "nineteen million, nine hundred seventy-one thousand, eight hundred fifty-seven".