644121447 has 4 divisors (see below), whose sum is σ = 858828600. Its totient is φ = 429414296.

The previous prime is 644121427. The next prime is 644121461. The reversal of 644121447 is 744121446.

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 644121447 - 2⁷ = 644121319 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644121427) 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, 107353572 + ... + 107353577.

It is an arithmetic number, because the mean of its divisors is an integer number (214707150).

Almost surely, 2^644121447 is an apocalyptic number.

644121447 is a deficient number, since it is larger than the sum of its proper divisors (214707153).

644121447 is a wasteful number, since it uses less digits than its factorization.

644121447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214707152.

The product of its digits is 21504, while the sum is 33.

The square root of 644121447 is about 25379.5478092105. The cubic root of 644121447 is about 863.6197918274.

Subtracting 644121447 from its reverse (744121446), we obtain a palindrome (99999999).

The spelling of 644121447 in words is "six hundred forty-four million, one hundred twenty-one thousand, four hundred forty-seven".