1289155391 has 4 divisors (see below), whose sum is σ = 1290310632. Its totient is φ = 1288000152.

The previous prime is 1289155381. The next prime is 1289155393. The reversal of 1289155391 is 1935519821.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1289155391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1289155393) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 575945 + ... + 578178.

It is an arithmetic number, because the mean of its divisors is an integer number (322577658).

Almost surely, 2^1289155391 is an apocalyptic number.

1289155391 is a deficient number, since it is larger than the sum of its proper divisors (1155241).

1289155391 is a wasteful number, since it uses less digits than its factorization.

1289155391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1155240.

The product of its digits is 97200, while the sum is 44.

The square root of 1289155391 is about 35904.8101373618. The cubic root of 1289155391 is about 1088.3496026237.

It can be divided in two parts, 128 and 9155391, that added together give a palindrome (9155519).

The spelling of 1289155391 in words is "one billion, two hundred eighty-nine million, one hundred fifty-five thousand, three hundred ninety-one".