821223649 has 3 divisors (see below), whose sum is σ = 821252307. Its totient is φ = 821194992.

The previous prime is 821223619. The next prime is 821223661. The reversal of 821223649 is 946322128.

It is a happy number.

The square root of 821223649 is 28657.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 164224225 + 656999424 = 12815^2 + 25632^2 .

It is a de Polignac number, because none of the positive numbers 2^k-821223649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821223619) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 14329 + ... + 42985.

It is an arithmetic number, because the mean of its divisors is an integer number (273750769).

Almost surely, 2^821223649 is an apocalyptic number.

821223649 is the 28657-th square number.

821223649 is the 14329-th centered octagonal number.

It is an amenable number.

821223649 is a deficient number, since it is larger than the sum of its proper divisors (28658).

821223649 is an frugal number, since it uses more digits than its factorization.

821223649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57314 (or 28657 counting only the distinct ones).

The product of its digits is 41472, while the sum is 37.

The cubic root of 821223649 is about 936.4555095471.

The spelling of 821223649 in words is "eight hundred twenty-one million, two hundred twenty-three thousand, six hundred forty-nine".