1281681818 has 4 divisors (see below), whose sum is σ = 1922522730. Its totient is φ = 640840908.

The previous prime is 1281681787. The next prime is 1281681823. The reversal of 1281681818 is 8181861821.

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

It can be written as a sum of positive squares in only one way, i.e., 1131447769 + 150234049 = 33637^2 + 12257^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320420453 + ... + 320420456.

Almost surely, 2^1281681818 is an apocalyptic number.

1281681818 is a deficient number, since it is larger than the sum of its proper divisors (640840912).

1281681818 is an equidigital number, since it uses as much as digits as its factorization.

1281681818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 640840911.

The product of its digits is 49152, while the sum is 44.

The square root of 1281681818 is about 35800.5840455152. The cubic root of 1281681818 is about 1086.2423756430.

The spelling of 1281681818 in words is "one billion, two hundred eighty-one million, six hundred eighty-one thousand, eight hundred eighteen".