642691 has 4 divisors (see below), whose sum is σ = 734512. Its totient is φ = 550872.

The previous prime is 642683. The next prime is 642701. The reversal of 642691 is 196246.

642691 = 300² + 301² + ... + 306².

642691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196246 = 2 ⋅98123.

It is not a de Polignac number, because 642691 - 2³ = 642683 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (642791) 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, 45900 + ... + 45913.

It is an arithmetic number, because the mean of its divisors is an integer number (183628).

2⁶⁴²⁶⁹¹ is an apocalyptic number.

642691 is a deficient number, since it is larger than the sum of its proper divisors (91821).

642691 is an equidigital number, since it uses as much as digits as its factorization.

642691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91820.

The product of its digits is 2592, while the sum is 28.

The square root of 642691 is about 801.6801107674. The cubic root of 642691 is about 86.2980017055.

The spelling of 642691 in words is "six hundred forty-two thousand, six hundred ninety-one".