644215 has 32 divisors (see below), whose sum is σ = 979776. Its totient is φ = 399360.

The previous prime is 644201. The next prime is 644227. The reversal of 644215 is 512446.

It is not a de Polignac number, because 644215 - 2⁹ = 643703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12129 + ... + 12181.

It is an arithmetic number, because the mean of its divisors is an integer number (30618).

2⁶⁴⁴²¹⁵ is an apocalyptic number.

644215 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

644215 is a deficient number, since it is larger than the sum of its proper divisors (335561).

644215 is a wasteful number, since it uses less digits than its factorization.

644215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99.

The product of its digits is 960, while the sum is 22.

The square root of 644215 is about 802.6300517673. The cubic root of 644215 is about 86.3661600874.

Subtracting from 644215 its reverse (512446), we obtain a square (131769 = 363²).

The spelling of 644215 in words is "six hundred forty-four thousand, two hundred fifteen".