642990 has 16 divisors (see below), whose sum is σ = 1543248. Its totient is φ = 171456.

The previous prime is 642977. The next prime is 642997. The reversal of 642990 is 99246.

It is a super-2 number, since 2×642990² = 826872280200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 21433 = 642990 / (6 + 4 + 2 + 9 + 9 + 0).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642997) by changing a digit.

642990 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10687 + ... + 10746.

It is an arithmetic number, because the mean of its divisors is an integer number (96453).

2⁶⁴²⁹⁹⁰ is an apocalyptic number.

642990 is an abundant number, since it is smaller than the sum of its proper divisors (900258).

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

642990 is a wasteful number, since it uses less digits than its factorization.

642990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21443.

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 642990 is about 801.8665724421. The cubic root of 642990 is about 86.3113824759.

The spelling of 642990 in words is "six hundred forty-two thousand, nine hundred ninety".