644725247 has 4 divisors (see below), whose sum is σ = 644777040. Its totient is φ = 644673456.

The previous prime is 644725217. The next prime is 644725253. The reversal of 644725247 is 742527446.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 644725247 - 2¹⁶ = 644659711 is a prime.

It is a super-2 number, since 2×644725247² = 831341288238422018, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644725217) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5318 + ... + 36300.

It is an arithmetic number, because the mean of its divisors is an integer number (161194260).

Almost surely, 2^644725247 is an apocalyptic number.

644725247 is a deficient number, since it is larger than the sum of its proper divisors (51793).

644725247 is a wasteful number, since it uses less digits than its factorization.

644725247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51792.

The product of its digits is 376320, while the sum is 41.

The square root of 644725247 is about 25391.4404278292. The cubic root of 644725247 is about 863.8895601972.

The spelling of 644725247 in words is "six hundred forty-four million, seven hundred twenty-five thousand, two hundred forty-seven".