1287638861 has 2 divisors, whose sum is σ = 1287638862. Its totient is φ = 1287638860.

The previous prime is 1287638839. The next prime is 1287638879. The reversal of 1287638861 is 1688367821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 853749961 + 433888900 = 29219^2 + 20830^2 .

It is a cyclic number.

It is not a de Polignac number, because 1287638861 - 2¹⁴ = 1287622477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1287638801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 643819430 + 643819431.

It is an arithmetic number, because the mean of its divisors is an integer number (643819431).

Almost surely, 2^1287638861 is an apocalyptic number.

It is an amenable number.

1287638861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1287638861 is an equidigital number, since it uses as much as digits as its factorization.

1287638861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 774144, while the sum is 50.

The square root of 1287638861 is about 35883.6851647096. The cubic root of 1287638861 is about 1087.9226661283.

The spelling of 1287638861 in words is "one billion, two hundred eighty-seven million, six hundred thirty-eight thousand, eight hundred sixty-one".