821949813 has 48 divisors (see below), whose sum is σ = 1306983600. Its totient is φ = 497172480.

The previous prime is 821949809. The next prime is 821949853. The reversal of 821949813 is 318949128.

It can be written as a sum of positive squares in 8 ways, for example, as 70257924 + 751691889 = 8382^2 + 27417^2 .

It is not a de Polignac number, because 821949813 - 2² = 821949809 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821949853) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1281973 + ... + 1282613.

It is an arithmetic number, because the mean of its divisors is an integer number (27228825).

Almost surely, 2^821949813 is an apocalyptic number.

It is an amenable number.

821949813 is a deficient number, since it is larger than the sum of its proper divisors (485033787).

821949813 is a wasteful number, since it uses less digits than its factorization.

821949813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 727 (or 690 counting only the distinct ones).

The product of its digits is 124416, while the sum is 45.

The square root of 821949813 is about 28669.6671239831. The cubic root of 821949813 is about 936.7314473474.

The spelling of 821949813 in words is "eight hundred twenty-one million, nine hundred forty-nine thousand, eight hundred thirteen".