811281661 has 4 divisors (see below), whose sum is σ = 811708992. Its totient is φ = 810854332.

The previous prime is 811281649. The next prime is 811281671. The reversal of 811281661 is 166182118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 166182118 = 2 ⋅83091059.

It is a cyclic number.

It is not a de Polignac number, because 811281661 - 2⁵ = 811281629 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 (811281671) 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, 210805 + ... + 214618.

It is an arithmetic number, because the mean of its divisors is an integer number (202927248).

Almost surely, 2^811281661 is an apocalyptic number.

It is an amenable number.

811281661 is a deficient number, since it is larger than the sum of its proper divisors (427331).

811281661 is a wasteful number, since it uses less digits than its factorization.

811281661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427330.

The product of its digits is 4608, while the sum is 34.

The square root of 811281661 is about 28483.0065302103. The cubic root of 811281661 is about 932.6611493304.

The spelling of 811281661 in words is "eight hundred eleven million, two hundred eighty-one thousand, six hundred sixty-one".