19978831 has 2 divisors, whose sum is σ = 19978832. Its totient is φ = 19978830.

The previous prime is 19978817. The next prime is 19978837. The reversal of 19978831 is 13887991.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19978831 - 2⁹ = 19978319 is a prime.

It is a super-2 number, since 2×19978831² = 798307376253122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19978837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9989415 + 9989416.

It is an arithmetic number, because the mean of its divisors is an integer number (9989416).

Almost surely, 2^19978831 is an apocalyptic number.

19978831 is a deficient number, since it is larger than the sum of its proper divisors (1).

19978831 is an equidigital number, since it uses as much as digits as its factorization.

19978831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 46.

The square root of 19978831 is about 4469.7685622412. The cubic root of 19978831 is about 271.3459586731.

The spelling of 19978831 in words is "nineteen million, nine hundred seventy-eight thousand, eight hundred thirty-one".