821981497 has 4 divisors (see below), whose sum is σ = 822513700. Its totient is φ = 821449296.

The previous prime is 821981443. The next prime is 821981557. The reversal of 821981497 is 794189128.

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 525143056 + 296838441 = 22916^2 + 17229^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821981497 is a prime.

It is a super-2 number, since 2×821981497² = 1351307162820722018, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 821981497.

It is not an unprimeable number, because it can be changed into a prime (821985497) 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, 263778 + ... + 266875.

It is an arithmetic number, because the mean of its divisors is an integer number (205628425).

Almost surely, 2^821981497 is an apocalyptic number.

It is an amenable number.

821981497 is a deficient number, since it is larger than the sum of its proper divisors (532203).

821981497 is a wasteful number, since it uses less digits than its factorization.

821981497 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532202.

The product of its digits is 290304, while the sum is 49.

The square root of 821981497 is about 28670.2196887293. The cubic root of 821981497 is about 936.7434833693.

The spelling of 821981497 in words is "eight hundred twenty-one million, nine hundred eighty-one thousand, four hundred ninety-seven".