1281665531 has 4 divisors (see below), whose sum is σ = 1283250600. Its totient is φ = 1280080464.

The previous prime is 1281665477. The next prime is 1281665591. The reversal of 1281665531 is 1355661821.

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

It is a cyclic number.

It is not a de Polignac number, because 1281665531 - 2⁶ = 1281665467 is a prime.

It is a super-2 number, since 2×1281665531² = 3285333066707023922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1281665591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 791321 + ... + 792938.

It is an arithmetic number, because the mean of its divisors is an integer number (320812650).

Almost surely, 2^1281665531 is an apocalyptic number.

1281665531 is a deficient number, since it is larger than the sum of its proper divisors (1585069).

1281665531 is an equidigital number, since it uses as much as digits as its factorization.

1281665531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1585068.

The product of its digits is 43200, while the sum is 38.

The square root of 1281665531 is about 35800.3565764365. The cubic root of 1281665531 is about 1086.2377744738.

The spelling of 1281665531 in words is "one billion, two hundred eighty-one million, six hundred sixty-five thousand, five hundred thirty-one".