642815 has 4 divisors (see below), whose sum is σ = 771384. Its totient is φ = 514248.

The previous prime is 642809. The next prime is 642833. The reversal of 642815 is 518246.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 518246 = 2 ⋅259123.

It is a cyclic number.

It is not a de Polignac number, because 642815 - 2⁴ = 642799 is a prime.

It is a super-2 number, since 2×642815² = 826422248450, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 12 and base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64277 + ... + 64286.

It is an arithmetic number, because the mean of its divisors is an integer number (192846).

2⁶⁴²⁸¹⁵ is an apocalyptic number.

642815 is a deficient number, since it is larger than the sum of its proper divisors (128569).

642815 is a wasteful number, since it uses less digits than its factorization.

642815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128568.

The product of its digits is 1920, while the sum is 26.

The square root of 642815 is about 801.7574446178. The cubic root of 642815 is about 86.3035514249.

The spelling of 642815 in words is "six hundred forty-two thousand, eight hundred fifteen".