1287721189 has 2 divisors, whose sum is σ = 1287721190. Its totient is φ = 1287721188.

The previous prime is 1287721177. The next prime is 1287721213. The reversal of 1287721189 is 9811277821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1283788900 + 3932289 = 35830^2 + 1983^2 .

It is an emirp because it is prime and its reverse (9811277821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1287721189 - 2⁵ = 1287721157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1287721109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 643860594 + 643860595.

It is an arithmetic number, because the mean of its divisors is an integer number (643860595).

Almost surely, 2^1287721189 is an apocalyptic number.

It is an amenable number.

1287721189 is a deficient number, since it is larger than the sum of its proper divisors (1).

1287721189 is an equidigital number, since it uses as much as digits as its factorization.

1287721189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 112896, while the sum is 46.

The square root of 1287721189 is about 35884.8322972255. The cubic root of 1287721189 is about 1087.9458518706.

The spelling of 1287721189 in words is "one billion, two hundred eighty-seven million, seven hundred twenty-one thousand, one hundred eighty-nine".