642157894821 has 32 divisors (see below), whose sum is σ = 914772700800. Its totient is φ = 399292084224.

The previous prime is 642157894801. The next prime is 642157894883. The reversal of 642157894821 is 128498751246.

It is not a de Polignac number, because 642157894821 - 2¹⁷ = 642157763749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642157894801) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3192786 + ... + 3387948.

It is an arithmetic number, because the mean of its divisors is an integer number (28586646900).

Almost surely, 2^642157894821 is an apocalyptic number.

It is an amenable number.

642157894821 is a deficient number, since it is larger than the sum of its proper divisors (272614805979).

642157894821 is a wasteful number, since it uses less digits than its factorization.

642157894821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 195765.

The product of its digits is 7741440, while the sum is 57.

The spelling of 642157894821 in words is "six hundred forty-two billion, one hundred fifty-seven million, eight hundred ninety-four thousand, eight hundred twenty-one".