642398681 has 4 divisors (see below), whose sum is σ = 642903012. Its totient is φ = 641894352.

The previous prime is 642398663. The next prime is 642398689. The reversal of 642398681 is 186893246.

642398681 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.

It can be written as a sum of positive squares in 2 ways, for example, as 221533456 + 420865225 = 14884^2 + 20515^2 .

It is a cyclic number.

It is not a de Polignac number, because 642398681 - 2¹⁴ = 642382297 is a prime.

It is a super-2 number, since 2×642398681² = 825352130701079522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (642398689) 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, 250250 + ... + 252803.

It is an arithmetic number, because the mean of its divisors is an integer number (160725753).

Almost surely, 2^642398681 is an apocalyptic number.

It is an amenable number.

642398681 is a deficient number, since it is larger than the sum of its proper divisors (504331).

642398681 is a wasteful number, since it uses less digits than its factorization.

642398681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 504330.

The product of its digits is 497664, while the sum is 47.

The square root of 642398681 is about 25345.5850396080. The cubic root of 642398681 is about 862.8491590887.

The spelling of 642398681 in words is "six hundred forty-two million, three hundred ninety-eight thousand, six hundred eighty-one".