19978571 has 2 divisors, whose sum is σ = 19978572. Its totient is φ = 19978570.

The previous prime is 19978561. The next prime is 19978577. The reversal of 19978571 is 17587991.

It is a strong prime.

It is an emirp because it is prime and its reverse (17587991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19978571 - 2¹⁸ = 19716427 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19978577) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9989285 + 9989286.

It is an arithmetic number, because the mean of its divisors is an integer number (9989286).

Almost surely, 2^19978571 is an apocalyptic number.

19978571 is a deficient number, since it is larger than the sum of its proper divisors (1).

19978571 is an equidigital number, since it uses as much as digits as its factorization.

19978571 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 19978571 is about 4469.7394778667. The cubic root of 19978571 is about 271.3447815896.

The spelling of 19978571 in words is "nineteen million, nine hundred seventy-eight thousand, five hundred seventy-one".