821542220 has 24 divisors (see below), whose sum is σ = 1725784704. Its totient is φ = 328512896.

The previous prime is 821542193. The next prime is 821542223. The reversal of 821542220 is 22245128.

It is a self number, because there is not a number n which added to its sum of digits gives 821542220.

It is not an unprimeable number, because it can be changed into a prime (821542223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 104549 + ... + 112131.

It is an arithmetic number, because the mean of its divisors is an integer number (71907696).

Almost surely, 2^821542220 is an apocalyptic number.

It is an amenable number.

821542220 is an abundant number, since it is smaller than the sum of its proper divisors (904242484).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

821542220 is a wasteful number, since it uses less digits than its factorization.

821542220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13009 (or 13007 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 26.

The square root of 821542220 is about 28662.5578063089. The cubic root of 821542220 is about 936.5765845636.

Adding to 821542220 its reverse (22245128), we get a palindrome (843787348).

The spelling of 821542220 in words is "eight hundred twenty-one million, five hundred forty-two thousand, two hundred twenty".