644101405 has 8 divisors (see below), whose sum is σ = 773348184. Its totient is φ = 514996800.

The previous prime is 644101399. The next prime is 644101427. The reversal of 644101405 is 504101446.

It can be written as a sum of positive squares in 4 ways, for example, as 5579044 + 638522361 = 2362^2 + 25269^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644101405 - 2¹⁵ = 644068637 is a prime.

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 644101405.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25306 + ... + 43915.

It is an arithmetic number, because the mean of its divisors is an integer number (96668523).

Almost surely, 2^644101405 is an apocalyptic number.

It is an amenable number.

644101405 is a deficient number, since it is larger than the sum of its proper divisors (129246779).

644101405 is a wasteful number, since it uses less digits than its factorization.

644101405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71087.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 644101405 is about 25379.1529606486. The cubic root of 644101405 is about 863.6108344859.

The spelling of 644101405 in words is "six hundred forty-four million, one hundred one thousand, four hundred five".