644102421 has 4 divisors (see below), whose sum is σ = 858803232. Its totient is φ = 429401612.

The previous prime is 644102411. The next prime is 644102449. The reversal of 644102421 is 124201446.

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.

It is a cyclic number.

It is not a de Polignac number, because 644102421 - 2¹⁵ = 644069653 is a prime.

It is a super-2 number, since 2×644102421² = 829735857476122482, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644102391 and 644102400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644102411) 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 3 ways as a sum of consecutive naturals, for example, 107350401 + ... + 107350406.

It is an arithmetic number, because the mean of its divisors is an integer number (214700808).

Almost surely, 2^644102421 is an apocalyptic number.

It is an amenable number.

644102421 is a deficient number, since it is larger than the sum of its proper divisors (214700811).

644102421 is a wasteful number, since it uses less digits than its factorization.

644102421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214700810.

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 644102421 is about 25379.1729770692. The cubic root of 644102421 is about 863.6112885697.

Adding to 644102421 its reverse (124201446), we get a palindrome (768303867).

The spelling of 644102421 in words is "six hundred forty-four million, one hundred two thousand, four hundred twenty-one".