642646 has 4 divisors (see below), whose sum is σ = 963972. Its totient is φ = 321322.

The previous prime is 642623. The next prime is 642673. The reversal of 642646 is 646246.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 646246 = 2 ⋅323123.

It is a nialpdrome in base 15.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160660 + ... + 160663.

It is an arithmetic number, because the mean of its divisors is an integer number (240993).

2⁶⁴²⁶⁴⁶ is an apocalyptic number.

642646 is a deficient number, since it is larger than the sum of its proper divisors (321326).

642646 is a wasteful number, since it uses less digits than its factorization.

642646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321325.

The product of its digits is 6912, while the sum is 28.

The square root of 642646 is about 801.6520442187. The cubic root of 642646 is about 86.2959875179.

Subtracting 642646 from its reverse (646246), we obtain a square (3600 = 60²).

The spelling of 642646 in words is "six hundred forty-two thousand, six hundred forty-six".