821640238 has 32 divisors (see below), whose sum is σ = 1309167360. Its totient is φ = 386131200.

The previous prime is 821640233. The next prime is 821640283. The reversal of 821640238 is 832046128.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821640233) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 420163 + ... + 422113.

It is an arithmetic number, because the mean of its divisors is an integer number (40911480).

Almost surely, 2^821640238 is an apocalyptic number.

821640238 is a deficient number, since it is larger than the sum of its proper divisors (487527122).

821640238 is a wasteful number, since it uses less digits than its factorization.

821640238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2172.

The product of its (nonzero) digits is 18432, while the sum is 34.

The square root of 821640238 is about 28664.2676166687. The cubic root of 821640238 is about 936.6138306562.

The spelling of 821640238 in words is "eight hundred twenty-one million, six hundred forty thousand, two hundred thirty-eight".