20191987 has 2 divisors, whose sum is σ = 20191988. Its totient is φ = 20191986.

The previous prime is 20191931. The next prime is 20192023. The reversal of 20191987 is 78919102.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20191987 - 2¹⁹ = 19667699 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20191387) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10095993 + 10095994.

It is an arithmetic number, because the mean of its divisors is an integer number (10095994).

Almost surely, 2^20191987 is an apocalyptic number.

20191987 is a deficient number, since it is larger than the sum of its proper divisors (1).

20191987 is an equidigital number, since it uses as much as digits as its factorization.

20191987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 20191987 is about 4493.5494878770. The cubic root of 20191987 is about 272.3075520243.

The spelling of 20191987 in words is "twenty million, one hundred ninety-one thousand, nine hundred eighty-seven".