642690 has 48 divisors (see below), whose sum is σ = 1725048. Its totient is φ = 165888.

The previous prime is 642683. The next prime is 642701. The reversal of 642690 is 96246.

It can be written as a sum of positive squares in 4 ways, for example, as 558009 + 84681 = 747^2 + 291^2 .

It is a super-2 number, since 2×642690² = 826100872200, which contains 22 as substring.

It is a Curzon number.

It is a nialpdrome in base 15.

It is an unprimeable number.

642690 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 23 ways as a sum of consecutive naturals, for example, 3234 + ... + 3426.

2⁶⁴²⁶⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 642690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (862524).

642690 is an abundant number, since it is smaller than the sum of its proper divisors (1082358).

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

642690 is a wasteful number, since it uses less digits than its factorization.

642690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 642690 is about 801.6794870770. The cubic root of 642690 is about 86.2979569468.

The spelling of 642690 in words is "six hundred forty-two thousand, six hundred ninety".