644690829 has 4 divisors (see below), whose sum is σ = 859587776. Its totient is φ = 429793884.

The previous prime is 644690819. The next prime is 644690833. The reversal of 644690829 is 928096446.

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 not a de Polignac number, because 644690829 - 2⁹ = 644690317 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644690819) 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, 107448469 + ... + 107448474.

It is an arithmetic number, because the mean of its divisors is an integer number (214896944).

Almost surely, 2^644690829 is an apocalyptic number.

It is an amenable number.

644690829 is a deficient number, since it is larger than the sum of its proper divisors (214896947).

644690829 is a wasteful number, since it uses less digits than its factorization.

644690829 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214896946.

The product of its (nonzero) digits is 746496, while the sum is 48.

The square root of 644690829 is about 25390.7626707037. The cubic root of 644690829 is about 863.8741873025.

The spelling of 644690829 in words is "six hundred forty-four million, six hundred ninety thousand, eight hundred twenty-nine".