1287650981 has 2 divisors, whose sum is σ = 1287650982. Its totient is φ = 1287650980.

The previous prime is 1287650971. The next prime is 1287650993. The reversal of 1287650981 is 1890567821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1217661025 + 69989956 = 34895^2 + 8366^2 .

It is an emirp because it is prime and its reverse (1890567821) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1287650981 is a prime.

It is a super-2 number, since 2×1287650981² = 3316090097740524722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1287650911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 643825490 + 643825491.

It is an arithmetic number, because the mean of its divisors is an integer number (643825491).

Almost surely, 2^1287650981 is an apocalyptic number.

It is an amenable number.

1287650981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1287650981 is an equidigital number, since it uses as much as digits as its factorization.

1287650981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 241920, while the sum is 47.

The square root of 1287650981 is about 35883.8540432880. The cubic root of 1287650981 is about 1087.9260795029.

The spelling of 1287650981 in words is "one billion, two hundred eighty-seven million, six hundred fifty thousand, nine hundred eighty-one".