821763881 has 4 divisors (see below), whose sum is σ = 822338772. Its totient is φ = 821188992.

The previous prime is 821763863. The next prime is 821763913. The reversal of 821763881 is 188367128.

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

It can be written as a sum of positive squares in 2 ways, for example, as 567201856 + 254562025 = 23816^2 + 15955^2 .

It is a cyclic number.

It is not a de Polignac number, because 821763881 - 2¹⁴ = 821747497 is a prime.

It is a super-2 number, since 2×821763881² = 1350591752232364322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821765881) 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, 285296 + ... + 288161.

It is an arithmetic number, because the mean of its divisors is an integer number (205584693).

Almost surely, 2^821763881 is an apocalyptic number.

It is an amenable number.

821763881 is a deficient number, since it is larger than the sum of its proper divisors (574891).

821763881 is a wasteful number, since it uses less digits than its factorization.

821763881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 574890.

The product of its digits is 129024, while the sum is 44.

The square root of 821763881 is about 28666.4242799830. The cubic root of 821763881 is about 936.6608098287.

The spelling of 821763881 in words is "eight hundred twenty-one million, seven hundred sixty-three thousand, eight hundred eighty-one".