642028821 has 48 divisors (see below), whose sum is σ = 1019729088. Its totient is φ = 358176000.

The previous prime is 642028811. The next prime is 642028837. The reversal of 642028821 is 128820246.

It is a happy number.

It is not a de Polignac number, because 642028821 - 2¹¹ = 642026773 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642028811) 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, 1232041 + ... + 1232561.

It is an arithmetic number, because the mean of its divisors is an integer number (21244356).

Almost surely, 2^642028821 is an apocalyptic number.

It is an amenable number.

642028821 is a deficient number, since it is larger than the sum of its proper divisors (377700267).

642028821 is a wasteful number, since it uses less digits than its factorization.

642028821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 722 (or 715 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 33.

The square root of 642028821 is about 25338.2876493263. The cubic root of 642028821 is about 862.6835326297.

The spelling of 642028821 in words is "six hundred forty-two million, twenty-eight thousand, eight hundred twenty-one".