821971961 has 4 divisors (see below), whose sum is σ = 841087632. Its totient is φ = 802856292.

The previous prime is 821971949. The next prime is 821971987. The reversal of 821971961 is 169179128.

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 821971961 - 2¹⁰ = 821970937 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821971921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9557771 + ... + 9557856.

It is an arithmetic number, because the mean of its divisors is an integer number (210271908).

Almost surely, 2^821971961 is an apocalyptic number.

It is an amenable number.

821971961 is a deficient number, since it is larger than the sum of its proper divisors (19115671).

821971961 is a wasteful number, since it uses less digits than its factorization.

821971961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19115670.

The product of its digits is 54432, while the sum is 44.

The square root of 821971961 is about 28670.0533832778. The cubic root of 821971961 is about 936.7398608951.

The spelling of 821971961 in words is "eight hundred twenty-one million, nine hundred seventy-one thousand, nine hundred sixty-one".