644090 has 16 divisors (see below), whose sum is σ = 1199880. Its totient is φ = 248640.

The previous prime is 644089. The next prime is 644101. The reversal of 644090 is 90446.

It can be written as a sum of positive squares in 4 ways, for example, as 564001 + 80089 = 751^2 + 283^2 .

It is an Ulam number.

It is an unprimeable 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, 821 + ... + 1400.

2⁶⁴⁴⁰⁹⁰ is an apocalyptic number.

644090 is a deficient number, since it is larger than the sum of its proper divisors (555790).

644090 is a wasteful number, since it uses less digits than its factorization.

644090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2257.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 644090 is about 802.5521789890. The cubic root of 644090 is about 86.3605737183.

The spelling of 644090 in words is "six hundred forty-four thousand, ninety".