642755621 has 4 divisors (see below), whose sum is σ = 642820332. Its totient is φ = 642690912.

The previous prime is 642755611. The next prime is 642755627. The reversal of 642755621 is 126557246.

642755621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 537590596 + 105165025 = 23186^2 + 10255^2 .

It is a cyclic number.

It is not a de Polignac number, because 642755621 - 2¹⁰ = 642754597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642755627) 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, 13976 + ... + 38481.

It is an arithmetic number, because the mean of its divisors is an integer number (160705083).

Almost surely, 2^642755621 is an apocalyptic number.

It is an amenable number.

642755621 is a deficient number, since it is larger than the sum of its proper divisors (64711).

642755621 is a wasteful number, since it uses less digits than its factorization.

642755621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64710.

The product of its digits is 100800, while the sum is 38.

The square root of 642755621 is about 25352.6255247854. The cubic root of 642755621 is about 863.0089395921.

It can be divided in two parts, 64275 and 5621, that added together give a palindrome (69896).

The spelling of 642755621 in words is "six hundred forty-two million, seven hundred fifty-five thousand, six hundred twenty-one".