642816 has 90 divisors (see below), whose sum is σ = 1978592. Its totient is φ = 207360.

The previous prime is 642809. The next prime is 642833. The reversal of 642816 is 618246.

642816 is a `hidden beast` number, since 642 + 8 + 16 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

Its product of digits (2304) is a multiple of the sum of its prime divisors (36).

It is a self number, because there is not a number n which added to its sum of digits gives 642816.

It is a congruent number.

It is an unprimeable number.

642816 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 20721 + ... + 20751.

642816 is a Friedman number, since it can be written as 62*8*6^(4*1), using all its digits and the basic arithmetic operations.

2⁶⁴²⁸¹⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 642816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989296).

642816 is an abundant number, since it is smaller than the sum of its proper divisors (1335776).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

642816 is an equidigital number, since it uses as much as digits as its factorization.

642816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59 (or 36 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 642816 is about 801.7580682475. The cubic root of 642816 is about 86.3035961778.

The spelling of 642816 in words is "six hundred forty-two thousand, eight hundred sixteen".