644559559531 has 4 divisors (see below), whose sum is σ = 644694212232. Its totient is φ = 644424906832.

The previous prime is 644559559513. The next prime is 644559559537. The reversal of 644559559531 is 135955955446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644559559531 - 2¹⁵ = 644559526763 is a prime.

It is a super-2 number, since 2×644559559531² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644559559531.

It is not an unprimeable number, because it can be changed into a prime (644559559537) 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, 67319170 + ... + 67328743.

It is an arithmetic number, because the mean of its divisors is an integer number (161173553058).

Almost surely, 2^644559559531 is an apocalyptic number.

644559559531 is a deficient number, since it is larger than the sum of its proper divisors (134652701).

644559559531 is a wasteful number, since it uses less digits than its factorization.

644559559531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134652700.

The product of its digits is 72900000, while the sum is 61.

The spelling of 644559559531 in words is "six hundred forty-four billion, five hundred fifty-nine million, five hundred fifty-nine thousand, five hundred thirty-one".