821381638 has 48 divisors (see below), whose sum is σ = 1552576032. Its totient is φ = 319017600.

The previous prime is 821381633. The next prime is 821381641. The reversal of 821381638 is 836183128.

It is a self number, because there is not a number n which added to its sum of digits gives 821381638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821381633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 773628 + ... + 774688.

It is an arithmetic number, because the mean of its divisors is an integer number (32345334).

Almost surely, 2^821381638 is an apocalyptic number.

821381638 is a deficient number, since it is larger than the sum of its proper divisors (731194394).

821381638 is a wasteful number, since it uses less digits than its factorization.

821381638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1549 (or 1538 counting only the distinct ones).

The product of its digits is 55296, while the sum is 40.

The square root of 821381638 is about 28659.7564190626. The cubic root of 821381638 is about 936.5155582249.

The spelling of 821381638 in words is "eight hundred twenty-one million, three hundred eighty-one thousand, six hundred thirty-eight".