644142736 has 10 divisors (see below), whose sum is σ = 1248026582. Its totient is φ = 322071360.

The previous prime is 644142727. The next prime is 644142749. The reversal of 644142736 is 637241446.

It can be written as a sum of positive squares in only one way, i.e., 434472336 + 209670400 = 20844^2 + 14480^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644142695 and 644142704.

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 as a sum of consecutive naturals, namely, 20129445 + ... + 20129476.

Almost surely, 2^644142736 is an apocalyptic number.

It is an amenable number.

644142736 is a deficient number, since it is larger than the sum of its proper divisors (603883846).

644142736 is a wasteful number, since it uses less digits than its factorization.

644142736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40258929 (or 40258923 counting only the distinct ones).

The product of its digits is 96768, while the sum is 37.

The square root of 644142736 is about 25379.9672182609. The cubic root of 644142736 is about 863.6293062853.

It can be divided in two parts, 644 and 142736, that added together give a triangular number (143380 = T₅₃₅).

The spelling of 644142736 in words is "six hundred forty-four million, one hundred forty-two thousand, seven hundred thirty-six".