9161821 has 4 divisors (see below), whose sum is σ = 9168412. Its totient is φ = 9155232.

The previous prime is 9161809. The next prime is 9161837. The reversal of 9161821 is 1281619.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1281619 = 41 ⋅31259.

It can be written as a sum of positive squares in 2 ways, for example, as 3348900 + 5812921 = 1830^2 + 2411^2 .

It is a cyclic number.

It is not a de Polignac number, because 9161821 - 2⁷ = 9161693 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 9161821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9161891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 306 + ... + 4291.

It is an arithmetic number, because the mean of its divisors is an integer number (2292103).

Almost surely, 2^9161821 is an apocalyptic number.

It is an amenable number.

9161821 is a deficient number, since it is larger than the sum of its proper divisors (6591).

9161821 is a wasteful number, since it uses less digits than its factorization.

9161821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6590.

The product of its digits is 864, while the sum is 28.

The square root of 9161821 is about 3026.8500128021. The cubic root of 9161821 is about 209.2476555699.

The spelling of 9161821 in words is "nine million, one hundred sixty-one thousand, eight hundred twenty-one".