642778 has 8 divisors (see below), whose sum is σ = 967572. Its totient is φ = 320256.

The previous prime is 642769. The next prime is 642779. The reversal of 642778 is 877246.

It can be written as a sum of positive squares in 2 ways, for example, as 635209 + 7569 = 797^2 + 87^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an Ulam number.

It is a d-powerful number, because it can be written as 6³ + 4³ + 7² + 2¹⁹ + 7⁶ + 8³ .

It is not an unprimeable number, because it can be changed into a prime (642779) by changing a digit.

642778 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 3 ways as a sum of consecutive naturals, for example, 826 + ... + 1402.

2⁶⁴²⁷⁷⁸ is an apocalyptic number.

642778 is a deficient number, since it is larger than the sum of its proper divisors (324794).

642778 is a wasteful number, since it uses less digits than its factorization.

642778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1136.

The product of its digits is 18816, while the sum is 34.

The square root of 642778 is about 801.7343699755. The cubic root of 642778 is about 86.3018955349.

The spelling of 642778 in words is "six hundred forty-two thousand, seven hundred seventy-eight".