644899501 has 4 divisors (see below), whose sum is σ = 678841600. Its totient is φ = 610957404.

The previous prime is 644899487. The next prime is 644899517. The reversal of 644899501 is 105998446.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 105998446 = 2 ⋅52999223.

It is a cyclic number.

It is not a de Polignac number, because 644899501 - 2²⁵ = 611345069 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644899201) 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, 16971021 + ... + 16971058.

It is an arithmetic number, because the mean of its divisors is an integer number (169710400).

Almost surely, 2^644899501 is an apocalyptic number.

It is an amenable number.

644899501 is a deficient number, since it is larger than the sum of its proper divisors (33942099).

644899501 is a wasteful number, since it uses less digits than its factorization.

644899501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33942098.

The product of its (nonzero) digits is 311040, while the sum is 46.

The square root of 644899501 is about 25394.8715491928. The cubic root of 644899501 is about 863.9673828315.

The spelling of 644899501 in words is "six hundred forty-four million, eight hundred ninety-nine thousand, five hundred one".