644420426 has 32 divisors (see below), whose sum is σ = 1086901200. Its totient is φ = 284497920.

The previous prime is 644420423. The next prime is 644420443. The reversal of 644420426 is 624024446.

It can be written as a sum of positive squares in 8 ways, for example, as 222159025 + 422261401 = 14905^2 + 20549^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644420392 and 644420401.

It is not an unprimeable number, because it can be changed into a prime (644420423) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 78266 + ... + 86106.

Almost surely, 2^644420426 is an apocalyptic number.

644420426 is a deficient number, since it is larger than the sum of its proper divisors (442480774).

644420426 is a wasteful number, since it uses less digits than its factorization.

644420426 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7994.

The product of its (nonzero) digits is 36864, while the sum is 32.

The square root of 644420426 is about 25385.4372820324. The cubic root of 644420426 is about 863.7533920169.

The spelling of 644420426 in words is "six hundred forty-four million, four hundred twenty thousand, four hundred twenty-six".