821841981 has 4 divisors (see below), whose sum is σ = 1095789312. Its totient is φ = 547894652.

The previous prime is 821841919. The next prime is 821841983. The reversal of 821841981 is 189148128.

821841981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a cyclic number.

It is not a de Polignac number, because 821841981 - 2¹⁷ = 821710909 is a prime.

It is a super-2 number, since 2×821841981² = 1350848483468008722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821841983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136973661 + ... + 136973666.

It is an arithmetic number, because the mean of its divisors is an integer number (273947328).

Almost surely, 2^821841981 is an apocalyptic number.

It is an amenable number.

821841981 is a deficient number, since it is larger than the sum of its proper divisors (273947331).

821841981 is a wasteful number, since it uses less digits than its factorization.

821841981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273947330.

The product of its digits is 36864, while the sum is 42.

The square root of 821841981 is about 28667.7864684388. The cubic root of 821841981 is about 936.6904821363.

The spelling of 821841981 in words is "eight hundred twenty-one million, eight hundred forty-one thousand, nine hundred eighty-one".