644121401 has 16 divisors (see below), whose sum is σ = 803886720. Its totient is φ = 501396480.

The previous prime is 644121389. The next prime is 644121427. The reversal of 644121401 is 104121446.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644121401 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644121461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82265 + ... + 89753.

It is an arithmetic number, because the mean of its divisors is an integer number (50242920).

Almost surely, 2^644121401 is an apocalyptic number.

It is an amenable number.

644121401 is a deficient number, since it is larger than the sum of its proper divisors (159765319).

644121401 is a wasteful number, since it uses less digits than its factorization.

644121401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8624.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 644121401 is about 25379.5469029689. The cubic root of 644121401 is about 863.6197712689.

Adding to 644121401 its reverse (104121446), we get a palindrome (748242847).

The spelling of 644121401 in words is "six hundred forty-four million, one hundred twenty-one thousand, four hundred one".