644420022 has 16 divisors (see below), whose sum is σ = 1294190832. Its totient is φ = 213914880.

The previous prime is 644419987. The next prime is 644420027. The reversal of 644420022 is 220024446.

It is a junction number, because it is equal to n+sod(n) for n = 644419974 and 644420001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644420027) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 221383 + ... + 224274.

It is an arithmetic number, because the mean of its divisors is an integer number (80886927).

Almost surely, 2^644420022 is an apocalyptic number.

644420022 is an abundant number, since it is smaller than the sum of its proper divisors (649770810).

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

644420022 is a wasteful number, since it uses less digits than its factorization.

644420022 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445903.

The product of its (nonzero) digits is 3072, while the sum is 24.

The square root of 644420022 is about 25385.4293247130. The cubic root of 644420022 is about 863.7532115155.

Adding to 644420022 its reverse (220024446), we get a palindrome (864444468).

The spelling of 644420022 in words is "six hundred forty-four million, four hundred twenty thousand, twenty-two".