642801021 has 4 divisors (see below), whose sum is σ = 857068032. Its totient is φ = 428534012.

The previous prime is 642801017. The next prime is 642801031. The reversal of 642801021 is 120108246.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 642801021 - 2² = 642801017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 642800982 and 642801000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642801001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107133501 + ... + 107133506.

It is an arithmetic number, because the mean of its divisors is an integer number (214267008).

Almost surely, 2^642801021 is an apocalyptic number.

It is an amenable number.

642801021 is a deficient number, since it is larger than the sum of its proper divisors (214267011).

642801021 is a wasteful number, since it uses less digits than its factorization.

642801021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214267010.

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 642801021 is about 25353.5208797516. The cubic root of 642801021 is about 863.0292581922.

Adding to 642801021 its reverse (120108246), we get a palindrome (762909267).

The spelling of 642801021 in words is "six hundred forty-two million, eight hundred one thousand, twenty-one".