644552421 has 4 divisors (see below), whose sum is σ = 859403232. Its totient is φ = 429701612.

The previous prime is 644552411. The next prime is 644552429. The reversal of 644552421 is 124255446.

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 644552421 - 2¹¹ = 644550373 is a prime.

It is a super-3 number, since 3×644552421³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644552429) 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, 107425401 + ... + 107425406.

It is an arithmetic number, because the mean of its divisors is an integer number (214850808).

Almost surely, 2^644552421 is an apocalyptic number.

It is an amenable number.

644552421 is a deficient number, since it is larger than the sum of its proper divisors (214850811).

644552421 is a wasteful number, since it uses less digits than its factorization.

644552421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214850810.

The product of its digits is 38400, while the sum is 33.

The square root of 644552421 is about 25388.0369662564. The cubic root of 644552421 is about 863.8123614625.

The spelling of 644552421 in words is "six hundred forty-four million, five hundred fifty-two thousand, four hundred twenty-one".