815941821 has 4 divisors (see below), whose sum is σ = 1087922432. Its totient is φ = 543961212.

The previous prime is 815941817. The next prime is 815941823. The reversal of 815941821 is 128149518.

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.

It is not a de Polignac number, because 815941821 - 2² = 815941817 is a prime.

It is a super-3 number, since 3×815941821³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

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 815941821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (815941823) 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, 135990301 + ... + 135990306.

It is an arithmetic number, because the mean of its divisors is an integer number (271980608).

Almost surely, 2^815941821 is an apocalyptic number.

It is an amenable number.

815941821 is a deficient number, since it is larger than the sum of its proper divisors (271980611).

815941821 is a wasteful number, since it uses less digits than its factorization.

815941821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271980610.

The product of its digits is 23040, while the sum is 39.

The square root of 815941821 is about 28564.6953598319. The cubic root of 815941821 is about 934.4435366944.

The spelling of 815941821 in words is "eight hundred fifteen million, nine hundred forty-one thousand, eight hundred twenty-one".