644666436 has 36 divisors (see below), whose sum is σ = 1645717164. Its totient is φ = 212760000.

The previous prime is 644666419. The next prime is 644666437. The reversal of 644666436 is 634666446.

It can be written as a sum of positive squares in 2 ways, for example, as 440748036 + 203918400 = 20994^2 + 14280^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 644666391 and 644666400.

It is not an unprimeable number, because it can be changed into a prime (644666437) 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 11 ways as a sum of consecutive naturals, for example, 85015 + ... + 92286.

Almost surely, 2^644666436 is an apocalyptic number.

It is an amenable number.

644666436 is an abundant number, since it is smaller than the sum of its proper divisors (1001050728).

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

644666436 is a wasteful number, since it uses less digits than its factorization.

644666436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177412 (or 177407 counting only the distinct ones).

The product of its digits is 1492992, while the sum is 45.

The square root of 644666436 is about 25390.2823143028. The cubic root of 644666436 is about 863.8632917704.

The spelling of 644666436 in words is "six hundred forty-four million, six hundred sixty-six thousand, four hundred thirty-six".