644927749 has 4 divisors (see below), whose sum is σ = 658649664. Its totient is φ = 631205836.

The previous prime is 644927741. The next prime is 644927753. The reversal of 644927749 is 947729446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644927749 - 2³ = 644927741 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644927696 and 644927705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644927741) 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, 6860887 + ... + 6860980.

It is an arithmetic number, because the mean of its divisors is an integer number (164662416).

Almost surely, 2^644927749 is an apocalyptic number.

It is an amenable number.

644927749 is a deficient number, since it is larger than the sum of its proper divisors (13721915).

644927749 is a wasteful number, since it uses less digits than its factorization.

644927749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13721914.

The product of its digits is 3048192, while the sum is 52.

The square root of 644927749 is about 25395.4277183906. The cubic root of 644927749 is about 863.9799971971.

The spelling of 644927749 in words is "six hundred forty-four million, nine hundred twenty-seven thousand, seven hundred forty-nine".