189787981 has 2 divisors, whose sum is σ = 189787982. Its totient is φ = 189787980.

The previous prime is 189787967. The next prime is 189787991.

189787981 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 175986756 + 13801225 = 13266^2 + 3715^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 189787981 - 2⁹ = 189787469 is a prime.

It is a super-2 number, since 2×189787981² = 72038955464112722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (189787931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 94893990 + 94893991.

It is an arithmetic number, because the mean of its divisors is an integer number (94893991).

Almost surely, 2^189787981 is an apocalyptic number.

It is an amenable number.

189787981 is a deficient number, since it is larger than the sum of its proper divisors (1).

189787981 is an equidigital number, since it uses as much as digits as its factorization.

189787981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2032128, while the sum is 58.

The square root of 189787981 is about 13776.3558679355. The cubic root of 189787981 is about 574.6757905142.

The spelling of 189787981 in words is "one hundred eighty-nine million, seven hundred eighty-seven thousand, nine hundred eighty-one".