642391 has 4 divisors (see below), whose sum is σ = 652984. Its totient is φ = 631800.

The previous prime is 642373. The next prime is 642403. The reversal of 642391 is 193246.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 642391 - 2⁵ = 642359 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642361) 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, 5205 + ... + 5326.

It is an arithmetic number, because the mean of its divisors is an integer number (163246).

2⁶⁴²³⁹¹ is an apocalyptic number.

642391 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

642391 is a deficient number, since it is larger than the sum of its proper divisors (10593).

642391 is a wasteful number, since it uses less digits than its factorization.

642391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10592.

The product of its digits is 1296, while the sum is 25.

The square root of 642391 is about 801.4929818782. The cubic root of 642391 is about 86.2845720118.

The spelling of 642391 in words is "six hundred forty-two thousand, three hundred ninety-one".