971821 has 2 divisors, whose sum is σ = 971822. Its totient is φ = 971820.

The previous prime is 971783. The next prime is 971833. The reversal of 971821 is 128179.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 617796 + 354025 = 786^2 + 595^2 .

It is a cyclic number.

It is not a de Polignac number, because 971821 - 2⁷ = 971693 is a prime.

971821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 971821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (971851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 485910 + 485911.

It is an arithmetic number, because the mean of its divisors is an integer number (485911).

2⁹⁷¹⁸²¹ is an apocalyptic number.

It is an amenable number.

971821 is a deficient number, since it is larger than the sum of its proper divisors (1).

971821 is an equidigital number, since it uses as much as digits as its factorization.

971821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 28.

The square root of 971821 is about 985.8098193871. The cubic root of 971821 is about 99.0517363839.

The spelling of 971821 in words is "nine hundred seventy-one thousand, eight hundred twenty-one".