821719861 has 2 divisors, whose sum is σ = 821719862. Its totient is φ = 821719860.

The previous prime is 821719831. The next prime is 821719891. The reversal of 821719861 is 168917128.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (821719831) and next prime (821719891).

It can be written as a sum of positive squares in only one way, i.e., 821682225 + 37636 = 28665^2 + 194^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821719861 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821719831) 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 as a sum of consecutive naturals, namely, 410859930 + 410859931.

It is an arithmetic number, because the mean of its divisors is an integer number (410859931).

Almost surely, 2^821719861 is an apocalyptic number.

It is an amenable number.

821719861 is a deficient number, since it is larger than the sum of its proper divisors (1).

821719861 is an equidigital number, since it uses as much as digits as its factorization.

821719861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 43.

The square root of 821719861 is about 28665.6564725108. The cubic root of 821719861 is about 936.6440846087.

The spelling of 821719861 in words is "eight hundred twenty-one million, seven hundred nineteen thousand, eight hundred sixty-one".