1289646640 has 20 divisors (see below), whose sum is σ = 2998428624. Its totient is φ = 515858624.

The previous prime is 1289646637. The next prime is 1289646649. The reversal of 1289646640 is 466469821.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (1289646649) 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, 8060212 + ... + 8060371.

Almost surely, 2^1289646640 is an apocalyptic number.

1289646640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1289646640 is an abundant number, since it is smaller than the sum of its proper divisors (1708781984).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1289646640 is a wasteful number, since it uses less digits than its factorization.

1289646640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16120596 (or 16120590 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 46.

The square root of 1289646640 is about 35911.6504772476. The cubic root of 1289646640 is about 1088.4878282041.

It can be divided in two parts, 12896 and 46640, that added together give a square (59536 = 244²).

The spelling of 1289646640 in words is "one billion, two hundred eighty-nine million, six hundred forty-six thousand, six hundred forty".